linux-kernel - Re: [PATCH v2 01/13] mm: support madvise(MADV

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Date:	Wed, 4 Nov 2015 00:53:42 -0500
From:	Daniel Micay <danielmicay@...il.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Minchan Kim <minchan@...nel.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Michal Hocko <mhocko@...e.cz>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux API <linux-api@...r.kernel.org>, Jason Evans <je@...com>,
	Shaohua Li <shli@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	yalin.wang2010@...il.com, Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v2 01/13] mm: support madvise(MADV_FREE)

> In the common case it will be passed many pages by the allocator. There
> will still be a layer of purging logic on top of MADV_FREE but it can be
> much thinner than the current workarounds for MADV_DONTNEED. So the
> allocator would still be coalescing dirty ranges and only purging when
> the ratio of dirty:clean pages rises above some threshold. It would be
> able to weight the largest ranges for purging first rather than logic
> based on stuff like aging as is used for MADV_DONTNEED.

I would expect that jemalloc would just start putting the dirty ranges
into the usual pair of red-black trees (with coalescing) and then doing
purging starting from the largest spans to get back down below whatever
dirty:clean ratio it's trying to keep. Right now, it has all lots of
other logic to deal with this since each MADV_DONTNEED call results in
lots of zeroing and then page faults.


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