[lc-devel] About 2.4.21 stability

[Ero C. <er...@dk...>]

Hi,

I've notice that some words have been said on stability of the cc path
on 2.4.21. I have to say that I've been running cc on 2.4.21 in
production use for months now with no complaints on its stability.

I ported/fixed myself the patch for 2.4.19 (fixed it just so that
issuing a patch cmd won't give any errors). That version did however
have some 'fun' with the overcommit feature of the kernel. If a hungry
process allocated more memory than the system could really provide, the
whole box went down in a swap storm whenever the kernel figured out that
it could actually not really satisfy one the memory writes to pages
allocated but not reserved for the process (after all, that's the idea
of overcommit).

One "solution" (rather, a low quality fix) was to limit the maximum
memory per process to (in my case) 196MiB (I have more than that
physically), with the hope that if a single process wants more than
that, the kernel won't allocate more.
The problem would still exist if several applications would,
simultaneously, start behaving like that. But is something that has just
happened once under extreme machine load and could have been prevented
with lower memory limits.

I suppose, cc and overcommit don't exactly get along well, because a cc
'enabled' kernel will (probably) think that always has memory to give
away (because of the compression). But this you'll know better than me.

To fix the swap storm crashes the maximum process memory setting I
changed was on the file "include/asm/resource.h", namely the member
RLIMIT_AS to have a definite value, instead of RLIM_INFINITY.

I hope this info is of some use to somebody.

Regards,

--
Ero Carrera