[issue884] Performance/memory problems under filesystem IO load
sinknull at crater.dragonflybsd.org
Fri Dec 14 02:36:23 PST 2007
New submission from Hasso Tepper <hasso at estpak.ee>:
During testing drive with dd I noticed that there are serious performance
problems. Programs which need disk access, block for 10 and more seconds.
Sometimes they don't continue the work until dd is finished. Raw disk access
(ie not writing to file, but directly to the disk) is reported to be OK (I
can't test it myself).
All tests are done with this command:
dd if=/dev/zero of=./file bs=4096k count=1000
Syncing after each dd helps to reproduce it more reliably (cache?).
There is one more strange thing in running these tests. I looked at memory
stats in top before and after running dd.
Mem: 42M Active, 40M Inact, 95M Wired, 304K Cache, 53M Buf, 795M Free
Mem: 70M Active, 679M Inact, 175M Wired, 47M Cache, 109M Buf, 1752K Free
And as a side effect - I can't get my network interfaces up any more after
running dd - "em0: Could not setup receive strucutres".
title: Performance/memory problems under filesystem IO load
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