Messages in this thread | | | Date | Tue, 12 Aug 2003 11:36:11 -0700 | From | Ken Savage <> | Subject | High CPU load with kswapd and heavy disk I/O |
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Short version: ---------------- kernels 2.4.17 --> 2.4.21 Dual Athlon SMP system 4GB RAM, 2GB swap 3ware RAID, filled with millions of files across thousands of directories. reiserfs 3.6
The following command is guaranteed to lock out the box by activating kswapd to >95% CPU, blocking out pings, everything.
find /RAID/data/ -type f -mtime +180 | xargs rm
Details: ---------- Applying the rmap patch seems to prevent kswapd from hogging the CPU, but causes it to freeze up for some other reason. (The server is remote, so I can't view the console.) Likewise 2.6.0-test* causes freezeups. Mind you, the server is under a fair bit of CPU and disk load -- hundreds of processes/threads all actively running. I suspect something in rmap has made its way into 2.6 and our usage pattern is triggering the same fault in both places.
It appears as though the system is unable to efficiently clean up disk buffer memory when called on to do so. In the Documentation/, there is mention of a buffermem sysctl, but that's nowhere to be found. It's obviously been removed/replaced... Is there any way to limit the amount of buffer memory used by the system, that way if/when kswapd needs to reclaim it, there's very little work for it to do?
Admittedly, that's just masking the problem, as opposed to solving it. Any idea why kswapd is having such a tough go?? Known solutions for this problem?
TIA,
Ken
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