Re: Oops in __free_pages_ok (pre7-1) (Long) (backtrace)

[Rajagopal Ananthanarayanan <ananth@sgi.com>]

Rik van Riel wrote:
> 
> On Thu, 4 May 2000, Rajagopal Ananthanarayanan wrote:
> > Linus Torvalds wrote:
> 
> > > There might be other details like this lurking, but this looks like a good
> > > first try. Ananth, willing to give it a whirl?
> >
> > I haven't looked at the code, but I replaced the whole while (1)
> > loop with the new for(;;). Things still remain the same: when
> > running dbench VM starts killing processes.
> 
> I've been thinking about it some more. When we look
> carefully the killing is always accompanied by a sudden
> decrease in free memory (while kswapd could easily keep
> up a few seconds ago).

You may have something here. It's the burstiness of
the demand. One thing I haven't noticed here in linux-mm
is any approaches to throttle the demand (Or may be I haven't
looked enough). Why not keep requests for new pages unsatisfied
if the _rate_ of allocations exceeds the _rate_ of freeing
(through swap-out or through write-out [bdflush])?

Simple counters don't capture rates. We need deltas in
the last 'n' time intervals. Then, match the delta-A
(allocation) to delta-F (free). 

Just a thought,

ananth.
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