On 6/27/12 3:30 PM, Theodore Ts'o wrote: > On Tue, Jun 26, 2012 at 04:44:08PM -0400, Eric Sandeen wrote: >>> >>> I tried running this fio recipe on v3.3, which I think does a decent job of >>> emulating the situation (fallocate 1G, do random 1M writes into it, with >>> fsyncs after each): >>> >>> [test] >>> filename=testfile >>> rw=randwrite >>> size=1g >>> filesize=1g >>> bs=1024k >>> ioengine=sync >>> fallocate=1 >>> fsync=1 > > A better workload would be to use a blocksize of 4k. By using a > blocksize of 1024k, it's not surprising that the metadata overhead is > in the noise. > > Try something like this; this will cause the extent tree overhead to > be roughly equal to the data block I/O. > > [global] > rw=randwrite > size=128m > filesize=1g > bs=4k > ioengine=sync > fallocate=1 > fsync=1 > > [thread1] > filename=testfile Well, ok ... TBH I changed it to size=16m to finish in under 20m.... so here are the results: fallocate 1g, do 16m of 4k random IOs, sync after each: # for I in a b c; do rm -f testfile; echo 3 > /proc/sys/vm/drop_caches; fio tytso.fio | grep 2>&1 WRITE; done WRITE: io=16384KB, aggrb=154KB/s, minb=158KB/s, maxb=158KB/s, mint=105989msec, maxt=105989msec WRITE: io=16384KB, aggrb=163KB/s, minb=167KB/s, maxb=167KB/s, mint=99906msec, maxt=99906msec WRITE: io=16384KB, aggrb=176KB/s, minb=180KB/s, maxb=180KB/s, mint=92791msec, maxt=92791msec same, but overwrite pre-written 1g file (same as the expose-my-data option ;) # dd if=/dev/zero of=testfile bs=1M count=1024 # for I in a b c; do echo 3 > /proc/sys/vm/drop_caches; fio tytso.fio | grep 2>&1 WRITE; done WRITE: io=16384KB, aggrb=164KB/s, minb=168KB/s, maxb=168KB/s, mint=99515msec, maxt=99515msec WRITE: io=16384KB, aggrb=164KB/s, minb=168KB/s, maxb=168KB/s, mint=99371msec, maxt=99371msec WRITE: io=16384KB, aggrb=164KB/s, minb=168KB/s, maxb=168KB/s, mint=99677msec, maxt=99677msec so no great surprise, small synchronous 4k writes have terrible performance, but I'm still not seeing a lot of fallocate overhead. xfs, FWIW: # for I in a b c; do rm -f testfile; echo 3 > /proc/sys/vm/drop_caches; fio tytso.fio | grep 2>&1 WRITE; done WRITE: io=16384KB, aggrb=202KB/s, minb=207KB/s, maxb=207KB/s, mint=80980msec, maxt=80980msec WRITE: io=16384KB, aggrb=203KB/s, minb=208KB/s, maxb=208KB/s, mint=80508msec, maxt=80508msec WRITE: io=16384KB, aggrb=204KB/s, minb=208KB/s, maxb=208KB/s, mint=80291msec, maxt=80291msec # dd if=/dev/zero of=testfile bs=1M count=1024 # for I in a b c; do echo 3 > /proc/sys/vm/drop_caches; fio tytso.fio | grep 2>&1 WRITE; done WRITE: io=16384KB, aggrb=197KB/s, minb=202KB/s, maxb=202KB/s, mint=82869msec, maxt=82869msec WRITE: io=16384KB, aggrb=203KB/s, minb=208KB/s, maxb=208KB/s, mint=80348msec, maxt=80348msec WRITE: io=16384KB, aggrb=202KB/s, minb=207KB/s, maxb=207KB/s, mint=80827msec, maxt=80827msec Again, I think this is just a diabolical workload ;) -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
