Cc: Peter Zijlstra <a.p.zijlstra@...>, <linux-kernel@...>, <linux-mm@...>, Thomas Graf <tgraf@...>, David Miller <davem@...>, Andrew Morton <akpm@...>, Daniel Phillips <phillips@...>, Pekka Enberg <penberg@...>
On Thu, May 17, 2007 at 10:29:06AM -0700, Christoph Lameter wrote:
Because it's a failsafe.
Simply stated, the problem is sometimes it's impossible to free memory
without allocating more memory. Thus we must keep enough protected
reserve that we can guarantee progress. This is what mempools are for
in the regular I/O stack. Unfortunately, mempools are a bad match for
network I/O.
It's absolutely correct that performance doesn't matter in the case
this patch is addressing. All that matters is digging ourselves out of
OOM. The box either survives the crisis or it doesn't.
It's also correct that we should hardly ever get into a situation
where we trigger this problem. But such cases are still fairly easy to
trigger in some workloads. Swap over network is an excellent example,
because we typically don't start swapping heavily until we're quite
low on freeable memory.
--
Mathematics is the supreme nostalgia of our time.
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