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>
55 lines
1.5 KiB
Plaintext
55 lines
1.5 KiB
Plaintext
QA output created by 089
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=== Testing nested image formats ===
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Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
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wrote 512/512 bytes at offset 0
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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wrote 512/512 bytes at offset 512
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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wrote 512/512 bytes at offset 1024
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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read 512/512 bytes at offset 0
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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read 512/512 bytes at offset 512
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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read 512/512 bytes at offset 1024
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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Pattern verification failed at offset 0, 512 bytes
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read 512/512 bytes at offset 0
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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=== Testing blkdebug ===
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
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wrote 512/512 bytes at offset 229376
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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read failed: Input/output error
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=== Testing qemu-img info output ===
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image: TEST_DIR/t.IMGFMT
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file format: IMGFMT
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virtual size: 64M (67108864 bytes)
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cluster_size: 65536
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=== Testing option merging ===
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format name: IMGFMT
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cluster size: 64 KiB
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vm state offset: 512 MiB
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Format specific information:
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compat: 1.1
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lazy refcounts: false
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refcount bits: 16
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corrupt: false
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format name: IMGFMT
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cluster size: 64 KiB
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vm state offset: 512 MiB
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Format specific information:
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compat: 1.1
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lazy refcounts: false
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refcount bits: 16
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corrupt: false
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*** done
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