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SubjectRe: OOM killer gripe (was Re: What still uses the block layer?)
Date
On Monday 15 October 2007 8:37:44 am Nick Piggin wrote:
> > Virtual memory isn't perfect. I've _always_ been able to come up with
> > examples where it just doesn't work for me. This doesn't mean VM
> > overcommit should be abolished, because it's useful more often than not.
>
> I hate to go completely offtopic here, but disks are so incredibly
> slow when compared to RAM that there is really nothing the kernel
> can do about this.

I know.

> Presumably the job will finish, given infinite
> time.

I gave it about half an hour, then it locked solid and stopped writing to the
disk at all. (I gave it another 5 minutes at that point, then held down the
power button.)

Lost about 50 open konqueror tabs...

> How much swap do you have configured?

2 gigs, same as ram.

> You really shouldn't configure
> so much unless you do want the kernel to actually use it all, right?

Two words: "Software suspend". I've actually been thinking of increasing it
on the next install...

> Because if we're not really conservative about OOM killing, then the
> user who actually really did want to use all the swap they configured
> gets angry when we kill their jobs without using it all.

I tend to lower "swappiness" and when that happens all sorts of stuff goes
weird. Software suspend used to say says it can't free enough memory if I
put swappiness at 0 (dunno if it still does). This time the OOM killer never
triggered before hard deadlock. (I think I had it around 20 or 40 or some
such.)

> Would an oom-kill-someone-now sysrq be of help, I wonder?

*shrug* It might. I was a letting it run hoping it would complete itself when
it locked solid. (The keyboard LEDs weren't flashing, so I don't _think_ it
paniced. I was in X so I wouldn't have seen a message...)

(To be honest, I can never remember how to trigger sysrq on a laptop keyboard.
Presumably X won't intercept it the way it does alt-f1 and ctrl-alt-del...)

Rob
--
"One of my most productive days was throwing away 1000 lines of code."
- Ken Thompson.
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