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RE: VM problem: hdd thrash + hang



On Fri, 6 Jul 2001, Alon Altman wrote:

> On Fri, 6 Jul 2001, Haim Gelfenbeyn wrote:
> > I don't think this is VM problem... Look more like misbehaved program
> > running as root which allocates more and more memory .VM starts killing
> > processes when some resource gets scarse (I don't remember if it's CPU
> > time or virtual memory). Maybe you should look at sysstat, it will log
> > CPU and memory useage, and you will find what process goes out of hand
> > when it happens next time.
> >
> > Haim.
>
> Where can I find this 'sysstat'?

looks like this is it: http://perso.wanadoo.fr/sebastien.godard/

> On Fri, 6 Jul 2001, mulix wrote:
>
> > your machine is running out of memory, and the VM is trying to kill the
> > processes responsible for it (without much success, it appears). you can
> > do one of several things:
> >
> > * check which process is behaving badly, and ulimit(1) it in advance.

>   How can I know which process it is? Can a non-root porcess be the cause of
>   this as well?

looks like sysstat might be able to give you per process statistics.
check out sar's -x and -X options
http://perso.wanadoo.fr/sebastien.godard/use_sar.html#x_option

> > * upgrade to the latest kernel (2.4.6) and hope the VM heuristics are
> > better, so it only kills the offending process.

>   I'm currently using kernel 2.2.17, do you know that the VM heuristics are
> in-fact improved?

2.4.x is vastly improved from 2.2, *except* in the area of the VM. that
is not to say that the VM in 2.4 is bad, just that it's still being
tweaked. i'm personally very happy with it. check out for example the
recent kernel traffic discusion about the VM:
http://kt.zork.net/kernel-traffic/kt20010618_122.html#1

> > * add more swap (no need to make a swap partition, you can use a swap
> > file).
>   I have 192M of RAM and 128M of sawp, is this enough?

i would add at the very least another 128mb. more if the machine is
running as a server of any sort or running big compilations (i have a 1
gig swap partition, since the time i tried to compile ACE. took 2 and a
half days).

> On Fri, 6 Jul 2001, Dani Arbel wrote:
>
> > Alon,
> > If you are using a 2.4 kernel prior to 2.4.5 then you are a victim of its
> > VM problem. Upgrade to 2.4.5 .
> > Dani
>
>   Does this mean that 2.2 kernels don't have this problem?

shouldn't be having this one, but might be having others :)

-- 
mulix
http://www.advogato.com/person/mulix

linux/reboot.h: #define LINUX_REBOOT_MAGIC1 0xfee1dead


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