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Message-ID: <20071026174409.GA1573@elf.ucw.cz>
Date: Fri, 26 Oct 2007 19:44:09 +0200
From: Pavel Machek <pavel@....cz>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Christoph Lameter <clameter@....com>,
Daniel Phillips <phillips@...nq.net>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
dkegel@...gle.com, David Miller <davem@...emloft.net>,
Nick Piggin <npiggin@...e.de>
Subject: Re: [RFC 0/3] Recursive reclaim (on __PF_MEMALLOC)
Hi!
> > > or
> > >
> > > - have a global reserve and selectively serves sockets
> > > (what I've been doing)
> >
> > That is a scalability problem on large systems! Global means global
> > serialization, cacheline bouncing and possibly livelocks. If we get into
> > this global shortage then all cpus may end up taking the same locks
> > cycling thought the same allocation paths.
>
> Dude, breathe, these boxens of yours will never swap over network simply
> because you never configure swap.
>
> And, _no_, it does not necessarily mean global serialisation. By simply
> saying there must be N pages available I say nothing about on which node
> they should be available, and the way the watermarks work they will be
> evenly distributed over the appropriate zones.
Agreed. Scalability of emergency swapping reserved is simply
unimportant. Please, lets get swapping to _work_ first, then we can
make it faster.
No, I do not think we'll ever see a livelock on this.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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