OpenZFS 9337 - zfs get all is slow due to uncached metadata

This project's goal is to make read-heavy channel programs and zfs(1m)
administrative commands faster by caching all the metadata that they will
need in the dbuf layer. This will prevent the data from being evicted, so
that any future call to i.e. zfs get all won't have to go to disk (very
much). There are two parts:

The dbuf_metadata_cache. We identify what to put into the cache based on
the object type of each dbuf.  Caching objset properties os
{version,normalization,utf8only,casesensitivity} in the objset_t. The reason
these needed to be cached is that although they are queried frequently,
they aren't stored in a dbuf type which we can easily recognize and cache in
the dbuf layer; instead, we have to explicitly store them. There's already
existing infrastructure for maintaining cached properties in the objset
setup code, so I simply used that.

Performance Testing:

 - Disabled kmem_flags
 - Tuned dbuf_cache_max_bytes very low (128K)
 - Tuned zfs_arc_max very low (64M)

Created test pool with 400 filesystems, and 100 snapshots per filesystem.
Later on in testing, added 600 more filesystems (with no snapshots) to make
sure scaling didn't look different between snapshots and filesystems.

Results:

    | Test                   | Time (trunk / diff) | I/Os (trunk / diff) |
    +------------------------+---------------------+---------------------+
    | zpool import           |     0:05 / 0:06     |    12.9k / 12.9k    |
    | zfs get all (uncached) |     1:36 / 0:53     |    16.7k / 5.7k     |
    | zfs get all (cached)   |     1:36 / 0:51     |    16.0k / 6.0k     |

Authored by: Matthew Ahrens <[email protected]>
Reviewed by: Prakash Surya <[email protected]>
Reviewed by: George Wilson <[email protected]>
Reviewed by: Thomas Caputi <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Approved by: Richard Lowe <[email protected]>
Ported-by: Alek Pinchuk <[email protected]>
Signed-off-by: Alek Pinchuk <[email protected]>

OpenZFS-issue: https://illumos.org/issues/9337
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f
Closes #7668

1 files changed, 54 insertions, 54 deletions

diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
index 1cb967641..0d2f03e22 100644
--- a/module/zfs/dmu.c
+++ b/module/zfs/dmu.c
@@ -81,60 +81,60 @@ int zfs_dmu_offset_next_sync = 0;
 int zfs_object_remap_one_indirect_delay_ticks = 0;
 
 const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
-	{ DMU_BSWAP_UINT8,	TRUE,	FALSE,	"unallocated"		},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"object directory"	},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"object array"		},
-	{ DMU_BSWAP_UINT8,	TRUE,	FALSE,	"packed nvlist"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"packed nvlist size"	},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"bpobj"			},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"bpobj header"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"SPA space map header"	},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"SPA space map"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	TRUE,	"ZIL intent log"	},
-	{ DMU_BSWAP_DNODE,	TRUE,	TRUE,	"DMU dnode"		},
-	{ DMU_BSWAP_OBJSET,	TRUE,	FALSE,	"DMU objset"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"DSL directory"		},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL directory child map"},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL dataset snap map"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL props"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"DSL dataset"		},
-	{ DMU_BSWAP_ZNODE,	TRUE,	FALSE,	"ZFS znode"		},
-	{ DMU_BSWAP_OLDACL,	TRUE,	TRUE,	"ZFS V0 ACL"		},
-	{ DMU_BSWAP_UINT8,	FALSE,	TRUE,	"ZFS plain file"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"ZFS directory"		},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"ZFS master node"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"ZFS delete queue"	},
-	{ DMU_BSWAP_UINT8,	FALSE,	TRUE,	"zvol object"		},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"zvol prop"		},
-	{ DMU_BSWAP_UINT8,	FALSE,	TRUE,	"other uint8[]"		},
-	{ DMU_BSWAP_UINT64,	FALSE,	TRUE,	"other uint64[]"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"other ZAP"		},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"persistent error log"	},
-	{ DMU_BSWAP_UINT8,	TRUE,	FALSE,	"SPA history"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"SPA history offsets"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"Pool properties"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL permissions"	},
-	{ DMU_BSWAP_ACL,	TRUE,	TRUE,	"ZFS ACL"		},
-	{ DMU_BSWAP_UINT8,	TRUE,	TRUE,	"ZFS SYSACL"		},
-	{ DMU_BSWAP_UINT8,	TRUE,	TRUE,	"FUID table"		},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"FUID table size"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL dataset next clones"},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"scan work queue"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"ZFS user/group/project used" },
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"ZFS user/group/project quota"},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"snapshot refcount tags"},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DDT ZAP algorithm"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DDT statistics"	},
-	{ DMU_BSWAP_UINT8,	TRUE,	TRUE,	"System attributes"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"SA master node"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"SA attr registration"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	TRUE,	"SA attr layouts"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"scan translations"	},
-	{ DMU_BSWAP_UINT8,	FALSE,	TRUE,	"deduplicated block"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL deadlist map"	},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"DSL deadlist map hdr"	},
-	{ DMU_BSWAP_ZAP,	TRUE,	FALSE,	"DSL dir clones"	},
-	{ DMU_BSWAP_UINT64,	TRUE,	FALSE,	"bpobj subobj"		}
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, FALSE, "unallocated"		},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "object directory"	},
+	{DMU_BSWAP_UINT64, TRUE,  TRUE,  FALSE, "object array"		},
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, FALSE, "packed nvlist"		},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "packed nvlist size"	},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "bpobj"			},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "bpobj header"		},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "SPA space map header"	},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "SPA space map"		},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, TRUE,  "ZIL intent log"	},
+	{DMU_BSWAP_DNODE,  TRUE,  FALSE, TRUE,  "DMU dnode"		},
+	{DMU_BSWAP_OBJSET, TRUE,  TRUE,  FALSE, "DMU objset"		},
+	{DMU_BSWAP_UINT64, TRUE,  TRUE,  FALSE, "DSL directory"		},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL directory child map"},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL dataset snap map"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL props"		},
+	{DMU_BSWAP_UINT64, TRUE,  TRUE,  FALSE, "DSL dataset"		},
+	{DMU_BSWAP_ZNODE,  TRUE,  FALSE, FALSE, "ZFS znode"		},
+	{DMU_BSWAP_OLDACL, TRUE,  FALSE, TRUE,  "ZFS V0 ACL"		},
+	{DMU_BSWAP_UINT8,  FALSE, FALSE, TRUE,  "ZFS plain file"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,  "ZFS directory"		},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "ZFS master node"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,  "ZFS delete queue"	},
+	{DMU_BSWAP_UINT8,  FALSE, FALSE, TRUE,  "zvol object"		},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "zvol prop"		},
+	{DMU_BSWAP_UINT8,  FALSE, FALSE, TRUE,  "other uint8[]"		},
+	{DMU_BSWAP_UINT64, FALSE, FALSE, TRUE,  "other uint64[]"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "other ZAP"		},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "persistent error log"	},
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, FALSE, "SPA history"		},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "SPA history offsets"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "Pool properties"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL permissions"	},
+	{DMU_BSWAP_ACL,    TRUE,  FALSE, TRUE,  "ZFS ACL"		},
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, TRUE,  "ZFS SYSACL"		},
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, TRUE,  "FUID table"		},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "FUID table size"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL dataset next clones"},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "scan work queue"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,  "ZFS user/group/project used" },
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,  "ZFS user/group/project quota"},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "snapshot refcount tags"},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "DDT ZAP algorithm"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "DDT statistics"	},
+	{DMU_BSWAP_UINT8,  TRUE,  FALSE, TRUE,	"System attributes"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,	"SA master node"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,	"SA attr registration"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, TRUE,	"SA attr layouts"	},
+	{DMU_BSWAP_ZAP,    TRUE,  FALSE, FALSE, "scan translations"	},
+	{DMU_BSWAP_UINT8,  FALSE, FALSE, TRUE,  "deduplicated block"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL deadlist map"	},
+	{DMU_BSWAP_UINT64, TRUE,  TRUE,  FALSE, "DSL deadlist map hdr"	},
+	{DMU_BSWAP_ZAP,    TRUE,  TRUE,  FALSE, "DSL dir clones"	},
+	{DMU_BSWAP_UINT64, TRUE,  FALSE, FALSE, "bpobj subobj"		}
 };
 
 const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {