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* Fix typos in include/Andrea Gelmini2019-08-301-1/+1
| | | | | | | Reviewed-by: Ryan Moeller <[email protected]> Reviewed-by: Richard Laager <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Andrea Gelmini <[email protected]> Closes #9238
* Cap metaslab memory usagePaul Dagnelie2019-08-161-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | On systems with large amounts of storage and high fragmentation, a huge amount of space can be used by storing metaslab range trees. Since metaslabs are only unloaded during a txg sync, and only if they have been inactive for 8 txgs, it is possible to get into a state where all of the system's memory is consumed by range trees and metaslabs, and txgs cannot sync. While ZFS knows how to evict ARC data when needed, it has no such mechanism for range tree data. This can result in boot hangs for some system configurations. First, we add the ability to unload metaslabs outside of syncing context. Second, we store a multilist of all loaded metaslabs, sorted by their selection txg, so we can quickly identify the oldest metaslabs. We use a multilist to reduce lock contention during heavy write workloads. Finally, we add logic that will unload a metaslab when we're loading a new metaslab, if we're using more than a certain fraction of the available memory on range trees. Reviewed-by: Matt Ahrens <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed-by: Sebastien Roy <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Paul Dagnelie <[email protected]> Closes #9128
* Linux 4.19-rc3+ compat: Remove refcount_t compatTim Schumacher2018-09-261-1/+1
| | | | | | | | | | | | | | | torvalds/linux@59b57717f ("blkcg: delay blkg destruction until after writeback has finished") added a refcount_t to the blkcg structure. Due to the refcount_t compatibility code, zfs_refcount_t was used by mistake. Resolve this by removing the compatibility code and replacing the occurrences of refcount_t with zfs_refcount_t. Reviewed-by: Franz Pletz <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tim Schumacher <[email protected]> Closes #7885 Closes #7932
* OpenZFS 9465 - ARC check for 'anon_size > arc_c/2' can stall the systemDon Brady2018-07-301-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | In the case of one pool being built on another pool, we want to make sure we don't end up throttling the lower (backing) pool when the upper pool is the majority contributor to dirty data. To insure we make forward progress during throttling, we also check the current pool's net dirty data and only throttle if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty data in the cache. Authored by: Don Brady <[email protected]> Reviewed by: Sebastien Roy <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Reviewed by: Prashanth Sreenivasa <[email protected]> Approved by: Robert Mustacchi <[email protected]> Ported-by: Brian Behlendorf <[email protected]> Porting Notes: * The new global variables zfs_arc_dirty_limit_percent, zfs_arc_anon_limit_percent, and zfs_arc_pool_dirty_percent were intentially not added as tunable module parameters. OpenZFS-issue: https://illumos.org/issues/9465 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d6a4c3ef Closes #7749
* Decryption error handling improvementsTom Caputi2018-03-311-1/+1
| | | | | | | | | | | | | | | | | | Currently, the decryption and block authentication code in the ZIO / ARC layers is a bit inconsistent with regards to the ereports that are produces and the error codes that are passed to calling functions. This patch ensures that all of these errors (which begin as ECKSUM) are converted to EIO before they leave the ZIO or ARC layer and that ereports are correctly generated on each decryption / authentication failure. In addition, this patch fixes a bug in zio_decrypt() where ECKSUM never gets written to zio->io_error. Reviewed by: Matt Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #7372
* Fix ARC hit rateBrian Behlendorf2018-01-081-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | When the compressed ARC feature was added in commit d3c2ae1 the method of reference counting in the ARC was modified. As part of this accounting change the arc_buf_add_ref() function was removed entirely. This would have be fine but the arc_buf_add_ref() function served a second undocumented purpose of updating the ARC access information when taking a hold on a dbuf. Without this logic in place a cached dbuf would not migrate its associated arc_buf_hdr_t to the MFU list. This would negatively impact the ARC hit rate, particularly on systems with a small ARC. This change reinstates the missing call to arc_access() from dbuf_hold() by implementing a new arc_buf_access() function. Reviewed-by: Giuseppe Di Natale <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Tim Chase <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed-by: George Melikov <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #6171 Closes #6852 Closes #6989
* Sequential scrub and resilversTom Caputi2017-11-151-19/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <[email protected]> Authored-by: Saso Kiselkov <[email protected]> Authored-by: Alek Pinchuk <[email protected]> Authored-by: Tom Caputi <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #3625 Closes #6256
* Scale the dbuf cache with arc_cchrisrd2017-09-291-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | Commit d3c2ae1 introduced a dbuf cache with a default size of the minimum of 100M or 1/32 maximum ARC size. (These figures may be adjusted using dbuf_cache_max_bytes and dbuf_cache_max_shift.) The dbuf cache is counted as metadata for the purposes of ARC size calculations. On a 1GB box the ARC maximum size defaults to c_max 493M which gives a dbuf cache default minimum size of 15.4M, and the ARC metadata defaults to minimum 16M. I.e. the dbuf cache is an significant proportion of the minimum metadata size. With other overheads involved this actually means the ARC metadata doesn't get down to the minimum. This patch dynamically scales the dbuf cache to the target ARC size instead of statically scaling it to the maximum ARC size. (The scale is still set by dbuf_cache_max_shift and the maximum size is still fixed by dbuf_cache_max_bytes.) Using the target ARC size rather than the current ARC size is done to help the ARC reach the target rather than simply focusing on the current size. Reviewed-by: Chunwei Chen <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: George Melikov <[email protected]> Signed-off-by: Chris Dunlop <[email protected]> Issue #6506 Closes #6561
* Native Encryption for ZFS on LinuxTom Caputi2017-08-141-14/+55
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This change incorporates three major pieces: The first change is a keystore that manages wrapping and encryption keys for encrypted datasets. These commands mostly involve manipulating the new DSL Crypto Key ZAP Objects that live in the MOS. Each encrypted dataset has its own DSL Crypto Key that is protected with a user's key. This level of indirection allows users to change their keys without re-encrypting their entire datasets. The change implements the new subcommands "zfs load-key", "zfs unload-key" and "zfs change-key" which allow the user to manage their encryption keys and settings. In addition, several new flags and properties have been added to allow dataset creation and to make mounting and unmounting more convenient. The second piece of this patch provides the ability to encrypt, decyrpt, and authenticate protected datasets. Each object set maintains a Merkel tree of Message Authentication Codes that protect the lower layers, similarly to how checksums are maintained. This part impacts the zio layer, which handles the actual encryption and generation of MACs, as well as the ARC and DMU, which need to be able to handle encrypted buffers and protected data. The last addition is the ability to do raw, encrypted sends and receives. The idea here is to send raw encrypted and compressed data and receive it exactly as is on a backup system. This means that the dataset on the receiving system is protected using the same user key that is in use on the sending side. By doing so, datasets can be efficiently backed up to an untrusted system without fear of data being compromised. Reviewed by: Matthew Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Jorgen Lundman <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #494 Closes #5769
* zfs_arc_num_sublists_per_state should be common to all multilistsMatthew Ahrens2017-02-151-2/+0
| | | | | | | | | | | | | The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <[email protected]> Reviewed-by: Dan Kimmel <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes #5764
* DLPX-44733 combine arc_buf_alloc_impl() with arc_buf_clone()Dan Kimmel2016-09-131-1/+1
| | | | | | | | Authored by: Dan Kimmel <[email protected]> Reviewed by: Tom Caputi <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Ported by: David Quigley <[email protected]> Issue #5078
* DLPX-40252 integrate EP-476 compressed zfs send/receiveDan Kimmel2016-09-131-3/+17
| | | | | | | | Authored by: Dan Kimmel <[email protected]> Reviewed by: Tom Caputi <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Ported by: David Quigley <[email protected]> Issue #5078
* OpenZFS 6950 - ARC should cache compressed dataGeorge Wilson2016-09-131-34/+59
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Authored by: George Wilson <[email protected]> Reviewed by: Prakash Surya <[email protected]> Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Reviewed by: Paul Dagnelie <[email protected]> Reviewed by: Tom Caputi <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Ported by: David Quigley <[email protected]> This review covers the reading and writing of compressed arc headers, sharing data between the arc_hdr_t and the arc_buf_t, and the implementation of a new dbuf cache to keep frequently access data uncompressed. I've added a new member to l1 arc hdr called b_pdata. The b_pdata always hangs off the arc_buf_hdr_t (if an L1 hdr is in use) and points to the physical block for that DVA. The physical block may or may not be compressed. If compressed arc is enabled and the block on-disk is compressed, then the b_pdata will match the block on-disk and remain compressed in memory. If the block on disk is not compressed, then neither will the b_pdata. Lastly, if compressed arc is disabled, then b_pdata will always be an uncompressed version of the on-disk block. Typically the arc will cache only the arc_buf_hdr_t and will aggressively evict any arc_buf_t's that are no longer referenced. This means that the arc will primarily have compressed blocks as the arc_buf_t's are considered overhead and are always uncompressed. When a consumer reads a block we first look to see if the arc_buf_hdr_t is cached. If the hdr is cached then we allocate a new arc_buf_t and decompress the b_pdata contents into the arc_buf_t's b_data. If the hdr already has a arc_buf_t, then we will allocate an additional arc_buf_t and bcopy the uncompressed contents from the first arc_buf_t to the new one. Writing to the compressed arc requires that we first discard the b_pdata since the physical block is about to be rewritten. The new data contents will be passed in via an arc_buf_t (uncompressed) and during the I/O pipeline stages we will copy the physical block contents to a newly allocated b_pdata. When an l2arc is inuse it will also take advantage of the b_pdata. Now the l2arc will always write the contents of b_pdata to the l2arc. This means that when compressed arc is enabled that the l2arc blocks are identical to those stored in the main data pool. This provides a significant advantage since we can leverage the bp's checksum when reading from the l2arc to determine if the contents are valid. If the compressed arc is disabled, then we must first transform the read block to look like the physical block in the main data pool before comparing the checksum and determining it's valid. OpenZFS-issue: https://www.illumos.org/issues/6950 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7fc10f0 Issue #5078
* Limit the amount of dnode metadata in the ARCTim Chase2016-07-251-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #4345 Issue #4512 Issue #4773 Closes #4858
* OpenZFS 6513 - partially filled holes lose birth timePaul Dagnelie2016-06-211-4/+6
| | | | | | | | | | | | | | | | | | | | Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Boris Protopopov <[email protected]> Approved by: Richard Lowe <[email protected]>a Ported by: Boris Protopopov <[email protected]> Signed-off-by: Boris Protopopov <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> OpenZFS-issue: https://www.illumos.org/issues/6513 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/8df0bcf0 If a ZFS object contains a hole at level one, and then a data block is created at level 0 underneath that l1 block, l0 holes will be created. However, these l0 holes do not have the birth time property set; as a result, incremental sends will not send those holes. Fix is to modify the dbuf_read code to fill in birth time data.
* Illumos 5987 - zfs prefetch code needs workMatthew Ahrens2016-01-121-12/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Paul Dagnelie <[email protected]> Approved by: Gordon Ross <[email protected]> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth [email protected] Signed-off-by: Brian Behlendorf <[email protected]>
* Illumos 6214 - zpools going southArne Jansen2015-09-111-14/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | 6214 zpools going south Reviewed by: Igor Kozhukhov <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Dan McDonald <[email protected]> Reviewed by: Saso Kiselkov <[email protected]> References: https://www.illumos.org/issues/6214 http://cr.illumos.org/~webrev/sensille/6214_zpools_going_south/ Porting Notes: Reintroduce b_compress to the l2arc_buf_hdr_t. In commit b9541d6 the compression flags were moved to the generic b_flags in the arc_buf_hdr_t. This is a problem because l2arc_compress_buf() may manipulate the compression flags and this can only be done safely under the hash lock which is not held. See Illumos 6214 for a detailed analysis of the race. HDR_GET_COMPRESS() macro was removed from arc_buf_info(). Ported-by: Brian Behlendorf <[email protected]> Closes #3757
* Dbuf hash table should be sized as is the arc hash tableTim Chase2015-09-021-0/+3
| | | | | | | | | | | Commit 49ddb315066e372f31bda29a5c546a9eccc8b418 added the zfs_arc_average_blocksize parameter to allow control over the size of the arc hash table. The dbuf hash table's size should be determined similarly. Signed-off-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #3721
* Make arc_prune() asynchronousBrian Behlendorf2015-06-111-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | As described in the comment above arc_adapt_thread() it is critical that the arc_adapt_thread() function never sleep while holding a hash lock. This behavior was possible in the Linux implementation because the arc_prune() logic was implemented to be synchronous. Under illumos the analogous dnlc_reduce_cache() function is asynchronous. To address this the arc_do_user_prune() function is has been reworked in to two new functions as follows: * arc_prune_async() is an asynchronous implementation which dispatches the prune callback to be run by the system taskq. This makes it suitable to use in the context of the arc_adapt_thread(). * arc_prune() is a synchronous implementation which depends on the arc_prune_async() implementation but blocks until the outstanding callbacks complete. This is used in arc_kmem_reap_now() where it is safe, and expected, that memory will be freed. This patch additionally adds the zfs_arc_meta_strategy module option while allows the meta reclaim strategy to be configured. It defaults to a balanced strategy which has been proved to work well under Linux but the illumos meta-only strategy can be enabled. Signed-off-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]>
* Illumos 5497 - lock contention on arcs_mtxPrakash Surya2015-06-111-2/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Reviewed by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Richard Elling <[email protected]> Approved by: Dan McDonald <[email protected]> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]
* Illumos 5408 - managing ZFS cache devices requires lots of RAMChris Williamson2015-06-111-4/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 5408 managing ZFS cache devices requires lots of RAM Reviewed by: Christopher Siden <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Don Brady <[email protected]> Reviewed by: Josef 'Jeff' Sipek <[email protected]> Approved by: Garrett D'Amore <[email protected]> Porting notes: Due to the restructuring of the ARC-related structures, this patch conflicts with at least the following existing ZoL commits: 6e1d7276c94cbd7c2e19f9232f6ba4bafa62dbe0 Fix inaccurate arcstat_l2_hdr_size calculations The ARC_SPACE_HDRS constant no longer exists and has been somewhat equivalently replaced by HDR_L2ONLY_SIZE. e0b0ca983d6897bcddf05af2c0e5d01ff66f90db Add visibility in to cached dbufs The new layering of l{1,2}arc_buf_hdr_t within the arc_buf_hdr struct requires additional structure member names to be used when referencing the inner items. Also, the presence of L1 or L2 inner member is indicated by flags using the new HDR_HAS_L{1,2}HDR macros. Ported by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]>
* Illumos 5369 - arc flags should be an enumGeorge Wilson2015-06-111-10/+31
| | | | | | | | | | | | | | | | | 5369 arc flags should be an enum 5370 consistent arc_buf_hdr_t naming scheme Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Alex Reece <[email protected]> Reviewed by: Sebastien Roy <[email protected]> Reviewed by: Richard Elling <[email protected]> Approved by: Richard Lowe <[email protected]> Porting notes: ZoL has moved some ARC definitions into arc_impl.h. Signed-off-by: Brian Behlendorf <[email protected]> Ported by: Tim Chase <[email protected]>
* Handle block pointers with a corrupt logical sizeBrian Behlendorf2014-10-231-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | The general strategy used by ZFS to verify that blocks are valid is to checksum everything. This has the advantage of being extremely robust and generically applicable regardless of the contents of the block. If a blocks checksum is valid then its contents are trusted by the higher layers. This system works exceptionally well as long as bad data is never written with a valid checksum. If this does somehow occur due to a software bug or a memory bit-flip on a non-ECC system it may result in kernel panic. One such place where this could occur is if somehow the logical size stored in a block pointer exceeds the maximum block size. This will result in an attempt to allocate a buffer greater than the maximum block size causing a system panic. To prevent this from happening the arc_read() function has been updated to detect this specific case. If a block pointer with an invalid logical size is passed it will treat the block as if it contained a checksum error. Signed-off-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #2678
* Illumos 4631 - zvol_get_stats triggering too many readsMatthew Ahrens2014-08-201-2/+1
| | | | | | | | | | | | | | | | | | 4631 zvol_get_stats triggering too many reads Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Sebastien Roy <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Approved by: Dan McDonald <[email protected]> References: https://www.illumos.org/issues/4631 https://github.com/illumos/illumos-gate/commit/bbfa8ea Ported-by: Boris Protopopov <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #2612 Closes #2480
* Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_tMatthew Ahrens2014-08-061-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | 4914 zfs on-disk bookmark structure should be named *_phys_t Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Richard Lowe <[email protected]> Reviewed by: Saso Kiselkov <[email protected]> Approved by: Robert Mustacchi <[email protected]> References: https://www.illumos.org/issues/4914 https://github.com/illumos/illumos-gate/commit/7802d7b Porting notes: There were a number of zfsonlinux-specific uses of zbookmark_t which needed to be updated. This should reduce the likelihood of further problems like issue #2094 from occurring. Ported by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #2558
* Split "data_size" into "meta" and "data"Prakash Surya2014-02-211-0/+1
| | | | | | | | | | | | | | | | | Previously, the "data_size" field in the arcstats kstat contained the amount of cached "metadata" and "data" in the ARC. The problem is this then made it difficult to extract out just the "metadata" size, or just the "data" size. To make it easier to distinguish the two values, "data_size" has been modified to count only buffers of type ARC_BUFC_DATA, and "meta_size" was added to count only buffers of type ARC_BUFC_METADATA. If one wants the old "data_size" value, simply sum the new "data_size" and "meta_size" values. Signed-off-by: Prakash Surya <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #2110
* Prune metadata from ghost lists in arc_adjust_metaPrakash Surya2014-02-211-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | To maintain a strict limit on the metadata contained in the arc, while preventing the arc buffer headers from completely consuming the "arc_meta_used" space, we need to evict metadata buffers from the arc's ghost lists along with the regular lists. This change modifies arc_adjust_meta such that it more closely models the adjustments made in arc_adjust. "arc_meta_used" is used similarly to "arc_size", and "arc_meta_limit" is used similarly to "arc_c". Testing metadata intensive workloads (e.g. creating, copying, and removing millions of small files and/or directories) has shown this change to make a dramatic improvement to the hit rate maintained in the arc. While I think there is still room for improvement, this is a big step in the right direction. In addition, zpl_free_cached_objects was made into a no-op as I'm not yet sure how to properly implement that function. Signed-off-by: Prakash Surya <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #2110
* Illumos #4045 write throttle & i/o scheduler performance workMatthew Ahrens2013-12-061-8/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Ned Bass <[email protected]> Reviewed by: Brendan Gregg <[email protected]> Approved by: Robert Mustacchi <[email protected]> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1913
* Illumos #3112, #3113, #3114Matthew Ahrens2013-11-051-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 3112 ztest does not honor ZFS_DEBUG 3113 ztest should use watchpoints to protect frozen arc bufs 3114 some leaked nvlists in zfsdev_ioctl Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Matt Amdur <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Eric Schrock <[email protected]> References: https://www.illumos.org/issues/3112 https://www.illumos.org/issues/3113 https://www.illumos.org/issues/3114 illumos/illumos-gate@cd1c8b85eb30b568e9816221430c479ace7a559d The /proc/self/cmd watchpoint interface is specific to Solaris. Therefore, the #3113 implementation was reworked to use the more portable mprotect(2) system call. When the pages are watched they are marked read-only for protection. Any write to the protected address range immediately trigger a SIGSEGV. The pages are marked writable again when they are unwatched. Ported-by: Brian Behlendorf <[email protected]> Issue #1489
* Add visibility in to cached dbufsBrian Behlendorf2013-10-251-0/+31
| | | | | | | | | | | | | | | | | | | | | | | | Currently there is no mechanism to inspect which dbufs are being cached by the system. There are some coarse counters in arcstats by they only give a rough idea of what's being cached. This patch aims to improve the current situation by adding a new dbufs kstat. When read this new kstat will walk all cached dbufs linked in to the dbuf_hash. For each dbuf it will dump detailed information about the buffer. It will also dump additional information about the referenced arc buffer and its related dnode. This provides a more complete view in to exactly what is being cached. With this generic infrastructure in place utilities can be written to post-process the data to understand exactly how the caching is working. For example, the data could be processed to show a list of all cached dnodes and how much space they're consuming. Or a similar list could be generated based on dnode type. Many other ways to interpret the data exist based on what kinds of questions you're trying to answer. Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Prakash Surya <[email protected]>
* Illumos #3464Matthew Ahrens2013-09-041-1/+1
| | | | | | | | | | | | | | | | | 3464 zfs synctask code needs restructuring Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Garrett D'Amore <[email protected]> References: https://www.illumos.org/issues/3464 illumos/illumos-gate@3b2aab18808792cbd248a12f1edf139b89833c13 Ported-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1495
* Illumos #3137 L2ARC compressionSaso Kiselkov2013-08-081-3/+5
| | | | | | | | | | | | | | | | | | | | | | | 3137 L2ARC compression Reviewed by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Approved by: Dan McDonald <[email protected]> References: illumos/illumos-gate@aad02571bc59671aa3103bb070ae365f531b0b62 https://www.illumos.org/issues/3137 http://wiki.illumos.org/display/illumos/L2ARC+Compression Notes for Linux port: A l2arc_nocompress module option was added to prevent the compression of l2arc buffers regardless of how a dataset's compression property is set. This allows the legacy behavior to be preserved. Ported by: James H <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1379
* Remove arc_data_buf_alloc()/arc_data_buf_free()Richard Yao2013-08-011-2/+0
| | | | | | | | | | These functions are used in neither Illumos nor ZFSOnLinux. They appear to have been replaced by arc_buf_alloc()/arc_buf_free(), so lets remove them. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1614
* Illumos #3498 panic in arc_read()George Wilson2013-07-021-7/+1
| | | | | | | | | | | | | | 3498 panic in arc_read(): !refcount_is_zero(&pbuf->b_hdr->b_refcnt) Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Approved by: Richard Lowe <[email protected]> References: illumos/illumos-gate@1b912ec7100c10e7243bf0879af0fe580e08c73d https://www.illumos.org/issues/3498 Ported-by: Brian Behlendorf <[email protected]> Closes #1249
* Illumos #3805 arc shouldn't cache freed blocksMatthew Ahrens2013-06-201-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3805 arc shouldn't cache freed blocks Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Richard Elling <[email protected]> Reviewed by: Will Andrews <[email protected]> Approved by: Dan McDonald <[email protected]> References: illumos/illumos-gate@6e6d5868f52089b9026785bd90257a3d3f6e5ee2 https://www.illumos.org/issues/3805 ZFS should proactively evict freed blocks from the cache. On dcenter, we saw that we were caching ~256GB of metadata, while the pool only had <4GB of metadata on disk. We were wasting about half the system's RAM (252GB) on blocks that have been freed. Even though these freed blocks will never be used again, and thus will eventually be evicted, this causes us to use memory inefficiently for 2 reasons: 1. A block that is freed has no chance of being accessed again, but will be kept in memory preferentially to a block that was accessed before it (and is thus older) but has not been freed and thus has at least some chance of being accessed again. 2. We partition the ARC into several buckets: user data that has been accessed only once (MRU) metadata that has been accessed only once (MRU) user data that has been accessed more than once (MFU) metadata that has been accessed more than once (MFU) The user data vs metadata split is somewhat arbitrary, and the primary control on how much memory is used to cache data vs metadata is to simply try to keep the proportion the same as it has been in the past (each bucket "evicts against" itself). The secondary control is to evict data before evicting metadata. Because of this bucketing, we may end up with one bucket mostly containing freed blocks that are very old, while another bucket has more recently accessed, still-allocated blocks. Data in the useful bucket (with still-allocated blocks) may be evicted in preference to data in the useless bucket (with old, freed blocks). On dcenter, we saw that the MFU metadata bucket was 230MB, while the MFU data bucket was 27GB and the MRU metadata bucket was 256GB. However, the vast majority of data in the MRU metadata bucket (256GB) was freed blocks, and thus useless. Meanwhile, the MFU metadata bucket (230MB) was constantly evicting useful blocks that will be soon needed. The problem of cache segmentation is a larger problem that needs more investigation. However, if we stop caching freed blocks, it should reduce the impact of this more fundamental issue. Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1503
* Illumos #3145, #3212George Wilson2013-01-081-0/+1
| | | | | | | | | | | | | | | | | | | | | 3145 single-copy arc 3212 ztest: race condition between vdev_online() and spa_vdev_remove() Reviewed by: Matt Ahrens <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Eric Schrock <[email protected]> Reviewed by: Justin T. Gibbs <[email protected]> Approved by: Eric Schrock <[email protected]> References: illumos-gate/commit/9253d63df408bb48584e0b1abfcc24ef2472382e illumos changeset: 13840:97fd5cdf328a https://www.illumos.org/issues/3145 https://www.illumos.org/issues/3212 Ported-by: Brian Behlendorf <[email protected]> Closes #989 Closes #1137
* Fix zfs_write_limit_max integer size mismatch on 32-bit systemsRichard Yao2012-10-111-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit c409e4647f221ab724a0bd10c480ac95447203c3 introduced a number of module parameters. This required several types to be changed to accomidate the required module parameters Linux macros. Unfortunately, arc.c contained its own extern definition of the zfs_write_limit_max variable and its type was not updated to be consistent with its dsl_pool.c counterpart. If the variable had been properly marked extern in a common header, then gcc would have generated a warning and this would not have slipped through. The result of this was that the ARC unconditionally expected zfs_write_limit_max to be 64-bit. Unfortunately, the largest size integer module parameter that Linux supports is unsigned long, which varies in size depending on the host system's native word size. The effect was that on 32-bit systems, ARC incorrectly performed 64-bit operations on a 32-bit value by reading the neighboring 32 bits as the upper 32 bits of the 64-bit value. We correct that by changing the extern declaration to use the unsigned long type and move these extern definitions in to the common arc.h header. This should make ARC correctly treat zfs_write_limit_max as a 32-bit value on 32-bit systems. Reported-by: Jorgen Lundman <[email protected]> Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #749
* Linux 3.1 compat, super_block->s_shrinkBrian Behlendorf2012-01-111-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The Linux 3.1 kernel has introduced the concept of per-filesystem shrinkers which are directly assoicated with a super block. Prior to this change there was one shared global shrinker. The zfs code relied on being able to call the global shrinker when the arc_meta_limit was exceeded. This would cause the VFS to drop references on a fraction of the dentries in the dcache. The ARC could then safely reclaim the memory used by these entries and honor the arc_meta_limit. Unfortunately, when per-filesystem shrinkers were added the old interfaces were made unavailable. This change adds support to use the new per-filesystem shrinker interface so we can continue to honor the arc_meta_limit. The major benefit of the new interface is that we can now target only the zfs filesystem for dentry and inode pruning. Thus we can minimize any impact on the caching of other filesystems. In the context of making this change several other important issues related to managing the ARC were addressed, they include: * The dnlc_reduce_cache() function which was called by the ARC to drop dentries for the Posix layer was replaced with a generic zfs_prune_t callback. The ZPL layer now registers a callback to drop these dentries removing a layering violation which dates back to the Solaris code. This callback can also be used by other ARC consumers such as Lustre. arc_add_prune_callback() arc_remove_prune_callback() * The arc_reduce_dnlc_percent module option has been changed to arc_meta_prune for clarity. The dnlc functions are specific to Solaris's VFS and have already been largely eliminated already. The replacement tunable now represents the number of bytes the prune callback will request when invoked. * Less aggressively invoke the prune callback. We used to call this whenever we exceeded the arc_meta_limit however that's not strictly correct since it results in over zeleous reclaim of dentries and inodes. It is now only called once the arc_meta_limit is exceeded and every effort has been made to evict other data from the ARC cache. * More promptly manage exceeding the arc_meta_limit. When reading meta data in to the cache if a buffer was unable to be recycled notify the arc_reclaim thread to invoke the required prune. * Added arcstat_prune kstat which is incremented when the ARC is forced to request that a consumer prune its cache. Remember this will only occur when the ARC has no other choice. If it can evict buffers safely without invoking the prune callback it will. * This change is also expected to resolve the unexpect collapses of the ARC cache. This would occur because when exceeded just the arc_meta_limit reclaim presure would be excerted on the arc_c value via arc_shrink(). This effectively shrunk the entire cache when really we just needed to reclaim meta data. Signed-off-by: Brian Behlendorf <[email protected]> Closes #466 Closes #292
* Support custom build directories and move includesBrian Behlendorf2010-09-081-0/+142
One of the neat tricks an autoconf style project is capable of is allow configurion/building in a directory other than the source directory. The major advantage to this is that you can build the project various different ways while making changes in a single source tree. For example, this project is designed to work on various different Linux distributions each of which work slightly differently. This means that changes need to verified on each of those supported distributions perferably before the change is committed to the public git repo. Using nfs and custom build directories makes this much easier. I now have a single source tree in nfs mounted on several different systems each running a supported distribution. When I make a change to the source base I suspect may break things I can concurrently build from the same source on all the systems each in their own subdirectory. wget -c http://github.com/downloads/behlendorf/zfs/zfs-x.y.z.tar.gz tar -xzf zfs-x.y.z.tar.gz cd zfs-x-y-z ------------------------- run concurrently ---------------------- <ubuntu system> <fedora system> <debian system> <rhel6 system> mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6 cd ubuntu cd fedora cd debian cd rhel6 ../configure ../configure ../configure ../configure make make make make make check make check make check make check This change also moves many of the include headers from individual incude/sys directories under the modules directory in to a single top level include directory. This has the advantage of making the build rules cleaner and logically it makes a bit more sense.