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Re: Performance tuning



Andre Cameron wrote:

Hello,

I have a dual PII 300 box with 512mb of ram and UW2 SCSI drives.

The thing is running sendmail, apache, MySQL, IMAP, and some other misc things at times.

Looks like apache and MySQL are hogging up most of the memory and only leaving me about 70M.
Sceen Scarpe:
14:24:41 up 6 days, 23:56, 3 users, load average: 0.00, 0.00, 0.00
72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
CPU0 states: 0.1% user 0.0% system 0.0% nice 0.0% iowait 99.4% idle
CPU1 states: 0.3% user 0.2% system 0.0% nice 0.0% iowait 99.0% idle
Mem: 513228k av, 441628k used, 71600k free, 0k shrd, 92792k buff
298708k actv, 96k in_d, 8644k in_c
Swap: 1052216k av, 7568k used, 1044648k free 209188k cached

Nope. You've got 209188k and 92792k cached (swap and file cache respectively). Your system doesn't seem to be under any sort of memory pressure. The 71600k free is the current size of the free list, that is, unused memory -- it'll soon get soaked up into cache or by some other process that needs it.


You don't want free memory -- if it's free, it not being used. If the system needs memory for some running process then it'll reclaim it from the swap cache first, then the buffer cache, then by swapping out more processes. That hasn't happened -- you've got some tiny amount of actually used swap.

If you hit "M" in top you'll see processes sorted by memory and what you're most interested in is the RSS column -- resident set size. If you see a lot of disk traffic and a fair amount of swap space then you're running short of memory because you're swapping. And you're not.

jch




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