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author | Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> | 2021-12-17 17:46:54 +0100 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2022-01-14 12:03:16 +0100 |
commit | 96054c76ff2db74165385a69f234c57a6bbc941e (patch) | |
tree | 7426f47bd77a9a4153f2c88fd043947daf5580e8 /scripts/simpletrace.py | |
parent | 51cd8bddd63540514d44808f7920811439baa253 (diff) | |
download | qemu-96054c76ff2db74165385a69f234c57a6bbc941e.zip qemu-96054c76ff2db74165385a69f234c57a6bbc941e.tar.gz qemu-96054c76ff2db74165385a69f234c57a6bbc941e.tar.bz2 |
qemu-img: make is_allocated_sectors() more efficient
Consider the case when the whole buffer is zero and end is unaligned.
If i <= tail, we return 1 and do one unaligned WRITE, RMW happens.
If i > tail, we do on aligned WRITE_ZERO (or skip if target is zeroed)
and again one unaligned WRITE, RMW happens.
Let's do better: don't fragment the whole-zero buffer and report it as
ZERO: in case of zeroed target we just do nothing and avoid RMW. If
target is not zeroes, one unaligned WRITE_ZERO should not be much worse
than one unaligned WRITE.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211217164654.1184218-3-vsementsov@virtuozzo.com>
Tested-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'scripts/simpletrace.py')
0 files changed, 0 insertions, 0 deletions