Re: [URGENT ASSISTANCE REQUESTED] production machines dying

Rik van Riel (H.H.vanRiel@fys.ruu.nl)
Mon, 24 Nov 1997 23:17:40 +0100 (MET)


On Mon, 24 Nov 1997, Alan Cox wrote:

> > > CONFIG_IP_ALWAYS_DEFRAG=y
> > > CONFIG_IP_ACCT=y
> >
> > Linux has some problems with memory fragmentation, and using
> > the CONFIG_IP_ALWAYS_DEFRAG option might get the kernel
> > hanging in some network-memory-allocation loop...
>
> No. Its an atomic allocation. It'll fail. Always defrag is however
> an unusual option

Linux 2.1.[456]x have been known to hang when the slab
system tries to allocate an 8kb piece of memory when
the memory is so badly fragmented that there are only
1-page pieces available...

With Zlatko's patch integrated in my patch the fragmentation
is combatted, instead it now leads to swapping frenzy :(
Better than crashing, but still bad... We need a general
memory defragmenter, but for that we'll need a way to find
the pte of a physical page... Some kind of phys_to_virt without
knowing the PID ??

Rik.

----------
Send Linux memory-management wishes to me: I'm currently looking
for something to hack...