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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
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When debugging with tracepoints, we see string pointers:
zfs 3017 [006] 8878.728915: zfs:zfs_set__error: ffffffffa0eec3fc:3013:ffffffffa0ebcd60(): error 0x2
ffffffffa0e1ca43 spa_open_common (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa0e1cbe3 spa_open (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa0e6f6ef zfs_ioc_stable (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa0e6f2a9 zfsdev_ioctl (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffff811909dd do_vfs_ioctl ([kernel.kallsyms])
ffffffff81190c41 sys_ioctl ([kernel.kallsyms])
ffffffff8156e2e9 system_call_fastpath ([kernel.kallsyms])
7ff7d8be69c7 __GI___ioctl (/lib64/libc-2.19.so)
7ff7d90cac53 lzc_ioctl.constprop.3 (/lib64/libzfs_core.so.1.0.0)
636f695f637a6c00 [unknown] ([unknown])
Printing the actual strings is more convenient:
zfs 3461 [001] 10599.847692: zfs:zfs_set__error: spa.c:3013:spa_open_common(): error 0x2
ffffffffa116ba43 spa_open_common (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa116bbe3 spa_open (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa11be8df zfs_ioc_stable (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffffa11be499 zfsdev_ioctl (/lib/modules/3.12.21-gentoo-r1/extra/zfs/zfs.ko)
ffffffff811909dd do_vfs_ioctl ([kernel.kallsyms])
ffffffff81190c41 sys_ioctl ([kernel.kallsyms])
ffffffff8156e2e9 system_call_fastpath ([kernel.kallsyms])
7f11b843c9c7 __GI___ioctl (/lib64/libc-2.19.so)
7f11b8920c53 lzc_ioctl.constprop.3 (/lib64/libzfs_core.so.1.0.0)
636f695f637a6c00 [unknown] ([unknown])
A few other tracepoints have strings as well, so switch to printing
the actual string values at the same time.
Signed-off-by: Richard Yao <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #4212
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Signed-off-by: Frédéric VANNIÈRE <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #3546
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Older versions of GCC (e.g. GCC 4.4.7 on RHEL6) do not allow duplicate
typedef declarations with the same type. The trace.h header contains
some typedefs to avoid 'unknown type' errors for C files that haven't
declared the type in question. But this causes build failures for C
files that have already declared the type. Newer versions of GCC (e.g.
v4.6) allow duplicate typedefs with the same type unless pedantic error
checking is in force. To support the older versions we need to remove
the duplicate typedefs.
Removal of the typedefs means we can't built tracepoints code using
those types unless the required headers have been included. To
facilitate this, all tracepoint event declarations have been moved out
of trace.h into separate headers. Each new header is explicitly included
from the C file that uses the events defined therein. The trace.h header
is still indirectly included form zfs_context.h and provides the
implementation of the dprintf(), dbgmsg(), and SET_ERROR() interfaces.
This makes those interfaces readily available throughout the code base.
The macros that redefine DTRACE_PROBE* to use Linux tracepoints are also
still provided by trace.h, so it is a prerequisite for the other
trace_*.h headers.
These new Linux implementation-specific headers do introduce a small
divergence from upstream ZFS in several core C files, but this should
not present a significant maintenance burden.
Signed-off-by: Ned Bass <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #2953
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