mirror_zfs/include
Matthew Ahrens 2e5dc449c1 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 <mahrens@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Thomas Caputi <tcaputi@datto.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Richard Lowe <richlowe@richlowe.net>
Ported-by: Alek Pinchuk <apinchuk@datto.com>
Signed-off-by: Alek Pinchuk <apinchuk@datto.com>

OpenZFS-issue: https://illumos.org/issues/9337
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f
Closes #7668
2018-07-12 10:49:27 -07:00
..
linux Linux 4.14 compat: blk_queue_stackable() 2018-06-19 21:52:45 -07:00
spl Fix kernel unaligned access on sparc64 2018-07-11 13:10:40 -07:00
sys OpenZFS 9337 - zfs get all is slow due to uncached metadata 2018-07-12 10:49:27 -07:00
libnvpair.h Add JSON output support to channel programs 2018-03-19 12:40:58 -07:00
libuutil_common.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
libuutil_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
libuutil.h Correct cppcheck errors 2017-09-19 12:17:29 -07:00
libzfs_core.h OpenZFS 9166 - zfs storage pool checkpoint 2018-06-26 10:07:42 -07:00
libzfs_impl.h OpenZFS 7431 - ZFS Channel Programs 2018-02-08 15:28:18 -08:00
libzfs.h OpenZFS 9166 - zfs storage pool checkpoint 2018-06-26 10:07:42 -07:00
Makefile.am Update build system and packaging 2018-05-29 16:00:33 -07:00
thread_pool.h Add libtpool (thread pools) 2017-08-09 15:31:08 -07:00
zfeature_common.h OpenZFS 9238 - ZFS Spacemap Encoding V2 2018-07-05 12:02:34 -07:00
zfs_comutil.h OpenZFS 9337 - zfs get all is slow due to uncached metadata 2018-07-12 10:49:27 -07:00
zfs_deleg.h OpenZFS 7614, 9064 - zfs device evacuation/removal 2018-04-14 12:16:17 -07:00
zfs_fletcher.h DLPX-44812 integrate EP-220 large memory scalability 2016-11-29 14:34:27 -08:00
zfs_namecheck.h OpenZFS 9330 - stack overflow when creating a deeply nested dataset 2018-07-09 13:02:50 -07:00
zfs_prop.h Native Encryption for ZFS on Linux 2017-08-14 10:36:48 -07:00