diff options
| author | Evgeny Yakovlev <eyakovlev@virtuozzo.com> | 2016-07-18 22:39:52 +0300 |
|---|---|---|
| committer | John Snow <jsnow@redhat.com> | 2016-07-18 18:19:01 -0400 |
| commit | 3ff2f67a7c24183fcbcfe1332e5223ac6f96438c (patch) | |
| tree | 0566b03b137403c149b74395f4a397705fb47f8a /include | |
| parent | 2dd7e10d7c6ec6edbe610345cadd6ec82ee3e65f (diff) | |
| download | qemu-3ff2f67a7c24183fcbcfe1332e5223ac6f96438c.tar.gz | |
block: ignore flush requests when storage is clean
Some guests (win2008 server for example) do a lot of unnecessary
flushing when underlying media has not changed. This adds additional
overhead on host when calling fsync/fdatasync.
This change introduces a write generation scheme in BlockDriverState.
Current write generation is checked against last flushed generation to
avoid unnessesary flushes.
The problem with excessive flushing was found by a performance test
which does parallel directory tree creation (from 2 processes).
Results improved from 0.424 loops/sec to 0.432 loops/sec.
Each loop creates 10^3 directories with 10 files in each.
This affected some blkdebug testcases that were expecting error logs from
failure-injected flushes which are now skipped entirely
(tests 026 071 089).
This also affects the performance of block jobs and thus BLOCK_JOB_READY
events for driver-mirror and active block-commit commands now arrives
faster, before QMP send successfully returns to caller (tests 141 144).
Signed-off-by: Evgeny Yakovlev <eyakovlev@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1468870792-7411-5-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Fam Zheng <famz@redhat.com>
CC: John Snow <jsnow@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/block/block_int.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/block/block_int.h b/include/block/block_int.h index 805414619d..a6b13adb45 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -439,6 +439,11 @@ struct BlockDriverState { int copy_on_read; /* if nonzero, copy read backing sectors into image. note this is a reference count */ + CoQueue flush_queue; /* Serializing flush queue */ + unsigned int write_gen; /* Current data generation */ + unsigned int flush_started_gen; /* Generation for which flush has started */ + unsigned int flushed_gen; /* Flushed write generation */ + BlockDriver *drv; /* NULL means no media */ void *opaque; |