Re: [RFC][PATCH 2/9] deadlock prevention core

From: Andrew Morton
Date: Fri Aug 18 2006 - 02:10:25 EST

On Thu, 17 Aug 2006 16:53:01 -0700
Daniel Phillips <phillips@xxxxxxxxxx> wrote:

> Andrew Morton wrote:
> > Daniel Phillips <phillips@xxxxxxxxxx> wrote:
> >>What happened to the case where we just fill memory full of dirty file
> >>pages backed by a remote disk?
> >
> > Processes which are dirtying those pages throttle at
> > /proc/sys/vm/dirty_ratio% of memory dirty. So it is not possible to "fill"
> > memory with dirty pages. If the amount of physical memory which is dirty
> > exceeds 40%: bug.
> Hi Andrew,
> So we make 400 MB of a 1 GB system

by default - it's runtime configurable.

> unavailable for write caching just to
> get around the network receive starvation issue?

No, it's mainly to avoid latency: to prevent tasks which want to allocate
pages from getting stuck behind writeback.

> What happens if some in kernel user grabs 68% of kernel memory to do some
> very important thing, does this starvation avoidance scheme still work?

Well something has to give way. The process might get swapped out a bit,
or it might stall in the page allocator because of all the dirty memory.

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