[ILUG] Out of Memory

[Paul Jakma]

On Tue, 7 Mar 2000, David Murphy wrote:


> You are, however, arguing that A is acceptable. I'm arguing that it
> isn't.
> 

no i am not arguing that it is acceptable. I'm arguing that on linux you
have to (at present) take care to try avoid OOM, because as we both know
linux currently deadlocks (or hoses userspace if 2.2.14).

I'm saying currently you need to take more care with tuning on linux
than other OS's.

(not because other OS's avoid OOM better, but because they are cleverer
about hosing userspace than 2.2.14)

> Again, I've never heard of anyone doing that - certainly when it comes
> to Solaris, I've managed to hear about every other tunable in the
> kernel bar the "don't overcommit" one, but I'm sure someone can refer
> me to the appropriate documentation.
> 

i believe solaris has a 'hard' memory configuration which does exactly
those things.  (eg disable overcommit, require backing store).

> I'm starting to envision a "Smash 'n' Hammer" ILUG event with as many
> OSes as possible subjected to as many tests as possible 8)
> 

this is a real good idea. perhaps if people could write some OS torture
tests. I'd love to see this.

Linux 2.2.12 vs 2.2.14 vs 2.2.15 vs Sol 7 x86 vs Sol 7 SPARC vs
IRIX.. etc..

i don't deny that linux deals with OOM badly, however the implication
by assocation that linux gets into trouble quicker than other OS's i
find unproven at best, and a damm lie at worst. Linux's VM is not
broken.

> Solaris 2.4, wow, that's only, what, six years old?
> 

so i take it that problem is fixed? (people have been saying that linux
has been broken for 8 years.) To solaris' credit, when this happened i
had some files open that i needed to save. I managed to notify the admin
and he could telnet in, clear tempfs and allow me to carry on.

so fair play to sol 2.4 for that.

> Do please explain under what circumstances hardhanging is and
> advantage.
> 

that's not what i said. 

as i've said all along, you need to take more preventative measures with
linux. You need to anticipate expected reasonable memory use and set
limits accordingly, and same for swap.

The benefit is that Linux VM is lighter and faster (on UP) than the
likes of Solaris.. etc.. (not saying FreeBSD cause i don't know it).

-paul

[let's make this the longest thread in ilug history. Cause damm sure i'm
not giving up! :) ]