From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu, 8 Feb 2007 17:06:33 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
Subject: Re: Drop PageReclaim()
In-Reply-To: <20070208163953.ab2bd694.akpm@linux-foundation.org>
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To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hugh@veritas.com>, linux-mm@kvack.org
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On Thu, 8 Feb 2007, Andrew Morton wrote:

> I doubt it.  One would need to troll five-year-old changelogs and mailing
> list discussion, but iirc that rotation was a large win in certain
> workloads, preventing scanning meltdowns and general memory stress.

I'd expect trouble here because of the taking of a LRU lock per page. For 
large amounts of concurrent I/O this could be an issue.

> > One additional issue that is raised by the writeback pages remaining on 
> > the LRU lists is that we can get into the same livelock situation as with 
> > mlocked pages if we keep on skipping over writeback pages.
> 
> That's why we rotate the reclaimable pages back to the head-of-queue.

I think the reclaim writeout is one minor contributor here. If there are 
large amounts of writeback pages from f.e. streaming general I/O then we 
may run still into bad situations because we need to scan over them.



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