At 09:55 AM 2/2/2007, Kenny Dail wrote:
What's sad with these tests is it takes 2m15s to read all the data in 71570 individual files, and only 15s to do it in 1 file. Granted there's a bit of overhead from the shell script looping, but not *that* much! I wonder how these tests would go on a different file system. I'm currently using reiserfs.
actually the loop adds a lot of overhead: These commands were run right in a row so there is some speedup due to cacheing, So I repeted test a few times. Admittedly, this is a small maildir.
bash-2.05b# ls | wc 1009 1009 75500
bash-2.05b# time for x in
ls; do cat $x > /dev/null ; donereal 0m3.670s user 0m0.347s sys 0m1.508s bash-2.05b# time cat * > /dev/null
real 0m0.497s user 0m0.015s sys 0m0.071s bash-2.05b# time for x in
ls; do cat $x > /dev/null ; donereal 0m2.237s user 0m0.356s sys 0m1.435s bash-2.05b# time cat * > /dev/null
real 0m0.504s user 0m0.001s sys 0m0.086s bash-2.05b# time for x in
ls; do cat $x > /dev/null ; donereal 0m2.415s user 0m0.356s sys 0m1.550s
wow, that is a ton of extra overhead. I'm doing some testing on ext3 vs reiserfs with different options and it seems that a lot of it has to do with the filesystem and how well it handles tons of files in a directory.
What I've gotten so far using the same shell loop with 71569 small files in the dir. Between each test the mount was unmounted and remounted to clear cache. ext3 defaults: 12m3s (~400k/sec of writes going on) ext3 noatime: 11m31s (0kb/sec writes) ext3 noatime,nodiratime: 11m43s (0k/sec of writes)
reiserfs defaults: 13m35s (~500k/sec of writes) reiserfs noatime: 8m47s (0k/sec of writes) reiserfs noatime,nodiratime: 9m51s (0k/sec of writes) reiserfs noatime,nodiratime,notail: 9m59s (0k/sec writes)
The clear winner seems to be reiserfs with only the noatime option set. I don't know why nodiratime actually slows it down (i ran these tests multiple times to confirm it wasn't flukish results), but perhaps it's an optimization issue with reiserfs.
- Nate