Bug#695182: [RFC] Reproducible OOM with just a few sleeps

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > I understand that more RAM leaves less lowmem. What is unacceptable is
> > that PAE crashes or freezes with OOM: it should gracefully handle the
> > issue. Noting that (for a machine with 4GB or under) PAE fails where the
> > HIGHMEM4G kernel succeeds and survives.
> 
> You have found a delta, but you're not really making apples-to-apples
> comparisons.  The page tables (a huge consumer of lowmem in your bug
> reports) have much more overhead on a PAE kernel.  A process with a
> single page faulted in with PAE will take at least 4 pagetable pages
> (it's 7 in practice for me with sleeps).  It's 2 pages minimum (and in
> practice with sleeps) on HIGHMEM4G.
> 
> There's probably a bug here.  But, it's incredibly unlikely to be seen
> in practice on anything resembling a modern system.  The 'sleep' issue
> is easily worked around by upgrading to a 64-bit kernel, or using

Are you saying that HIGHMEM configuration with 4GB ram is not expected
to work?
									Pavel
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