tree 28e919ff6837081ddc1e6a32c4d325dc01f58586
parent 3f36aa6b73eb5730d7de716391dcf0735e886d10
author Steven Lang <tirea@google.com> 1328604179 +0100
committer Jens Axboe <axboe@kernel.dk> 1328604179 +0100

Optimize pattern verify

Similar to the patch last week, this optimizes the pattern verify
operation to use optimized library calls like memcmp(), and only fall
back to byte-by-byte if there is a miscompare to locate it.

This uses the same premise that the pattern is repeated as many times
as possible to do large compares in a single call.  For single byte
pattern, the setup fills the pattern space, and verify assumes it is
full.

Tested by running a script which created an 8k file with 4k bs and,
one byte at a time, tried corrupting the pattern and running a read
pass and verified it still found miscompares across the whole range of
the pattern.  This was done with a pattern length of 1 and 3 bytes.

In performance tests, this was about 8 times more efficient on
verifies than without this patch.

Signed-off-by: Jens Axboe <axboe@kernel.dk>