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block: ignore flush requests when storage is clean

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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>
This commit is contained in:
Evgeny Yakovlev 2016-07-18 22:39:52 +03:00 • committed by John Snow
parent 2dd7e10d7c
commit 3ff2f67a7c
9 changed files with 32 additions and 113 deletions
Download patch file Download diff file Expand all files Collapse all files

50
tests/qemu-iotests/026.out.nocache
View file

@ -14,7 +14,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_update; errno: 5; imm: off; once: off; write
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
@ -23,7 +22,6 @@ This means waste of disk space, but no harm to data.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_update; errno: 5; imm: off; once: off; write -b
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
@ -42,7 +40,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_update; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -51,7 +48,6 @@ This means waste of disk space, but no harm to data.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_update; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -78,11 +74,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l2_load; errno: 5; imm: off; once: off; write
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
read failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -90,11 +82,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l2_load; errno: 5; imm: off; once: off; write -b
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
read failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -118,11 +106,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l2_load; errno: 28; imm: off; once: off; write
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
read failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -130,11 +114,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l2_load; errno: 28; imm: off; once: off; write -b
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
read failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -314,14 +294,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_load; errno: 5; imm: off; once: off; write
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_load; errno: 5; imm: off; once: off; write -b
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
@ -338,14 +316,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_load; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_load; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
@ -362,14 +338,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_update_part; errno: 5; imm: off; once: off; write
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_update_part; errno: 5; imm: off; once: off; write -b
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
@ -386,14 +360,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_update_part; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_update_part; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
@ -410,14 +382,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc; errno: 5; imm: off; once: off; write
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc; errno: 5; imm: off; once: off; write -b
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
@ -434,14 +404,12 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
@ -458,15 +426,11 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: cluster_alloc; errno: 5; imm: off; once: off; write
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: cluster_alloc; errno: 5; imm: off; once: off; write -b
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -482,15 +446,11 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: cluster_alloc; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: cluster_alloc; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
@ -561,7 +521,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc_write_blocks; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -570,7 +529,6 @@ This means waste of disk space, but no harm to data.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc_write_blocks; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -589,7 +547,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc_write_table; errno: 28; imm: off; once: off; write
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -598,7 +555,6 @@ This means waste of disk space, but no harm to data.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: refblock_alloc_write_table; errno: 28; imm: off; once: off; write -b
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
@ -643,8 +599,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_grow_alloc_table; errno: 5; imm: off; once: off
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -655,8 +609,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_grow_alloc_table; errno: 28; imm: off; once: off
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
@ -667,7 +619,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_grow_write_table; errno: 5; imm: off; once: off
Failed to flush the L2 table cache: Input/output error
Failed to flush the refcount block cache: Input/output error
write failed: Input/output error
No errors were found on the image.
@ -679,7 +630,6 @@ No errors were found on the image.
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
Event: l1_grow_write_table; errno: 28; imm: off; once: off
Failed to flush the L2 table cache: No space left on device
Failed to flush the refcount block cache: No space left on device
write failed: No space left on device
No errors were found on the image.