Messages in this thread | | | Date | Sat, 20 Oct 2001 19:34:02 -0700 (PDT) | From | D Campbell <> | Subject | kswapd is CPU-hungry (kernel 2.4.2-2) |
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after searching the archives i'm still a bit concerned about the CPU usage of kswapd on a machine with lots of memory.
summary: kswapd at 66% CPU. 1G RAM. ~800M taken by ramdisks. no swap.
hardware: intel PIII-833 underclocked to 650 1G physical memory
memory config: 0.750 G ramdisk, ext2fs from an image, mounted as root 64 M additional ramdisk, ramfs, mounted as /tmp 8 M initrd, ext2fs from image, hangs around at /initrd
this should leave about 190M for applications and OS to play with, even when /tmp is full. it's running mysqld, sshd and a few simple data aquisition apps that use the SQL server. no X, no sendmail, no development envoronment. intuitively, should be OK.
once booted, the machine runs with no physical drives mounted. there is no swap partition or file.
top reports kswapd taking about 2/3 of what should be a fully loaded system.
12:15am up 1 day, 6:20, 3 users, load average: 4.04, 3.32, 2.92 58 processes: 54 sleeping, 4 running, 0 zombie, 0 stopped CPU states: 0.0% user, 68.5% system, 31.3% nice, 0.0% idle Mem: 1028808K av, 946404K used, 82404K free, 0K shrd, 794432K buff Swap: 0K av, 0K used, 0K free 38256K cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND 4 root 9 0 0 0 0 SW 68.4 0.0 1155m kswapd <-- 1265 root 20 19 244 244 168 R N 31.4 0.0 656:51 dnetc 1 root 8 0 108 108 36 S 0.0 0.0 0:05 init
i understand that without swapspace, all kswapd can do is knock bits of executables out of the program memory so they have to be read again from the ramdisk.
nice idea, but in practice it's being done much more aggressively than this user needs. no need to spend so much effort on keeping 80 M of RAM always free when nothing is likely to ask for that much.
the same kernel running on a more modest machine with some real swap space is fine:
30 processes: 27 sleeping, 3 running, 0 zombie, 0 stopped CPU states: 0.1% user, 0.3% system, 99.4% nice, 0.0% idle Mem: 126568K av, 125072K used, 1496K free, 0K shrd, 16484K buff Swap: 1976K av, 8K used, 1968K free 55392K cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND 11348 root 20 19 520 520 444 R N 99.4 0.4 13820m dnetc 23571 root 11 0 1004 1004 812 R 0.5 0.7 0:00 top
has bigram/bigramdisk been addressed any differently/better in 2.4.12 or earlier?
is there anything i can read from the machine to help show someone familiar with the vm code where it's being goofy?
is there something i can tweak to change kswapd's goals? /proc/sys/vm/freepages is read-only (mode 444) but the others are tweakable.
grazzi mucho.
Duncan. ( will search archives for replies, cc is welcome. )
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