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Date: Tue, 22 Aug 2017 14:24:08 -0700 From: Andi Kleen <ak@...ux.intel.com> To: Christopher Lameter <cl@...ux.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, "Liang, Kan" <kan.liang@...el.com>, Mel Gorman <mgorman@...hsingularity.net>, Mel Gorman <mgorman@...e.de>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>, Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>, linux-mm <linux-mm@...ck.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk On Tue, Aug 22, 2017 at 04:08:52PM -0500, Christopher Lameter wrote: > On Tue, 22 Aug 2017, Andi Kleen wrote: > > > We only see it on 4S+ today. But systems are always getting larger, > > so what's a large system today, will be a normal medium scale system > > tomorrow. > > > > BTW we also collected PT traces for the long hang cases, but it was > > hard to find a consistent pattern in them. > > Hmmm... Maybe it would be wise to limit the pages autonuma can migrate? > > If a page has more than 50 refcounts or so then dont migrate it. I think > high number of refcounts and a high frequewncy of calls are reached in > particular for pages of the c library. Attempting to migrate those does > not make much sense anyways because the load may shift and another > function may become popular. We may end up shifting very difficult to > migrate pages back and forth. I believe in this case it's used by threads, so a reference count limit wouldn't help. If migrating code was a problem I would probably rather just disable migration of read-only pages. -Andi
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