linux-kernel - Re: [PATCH 5/8] mm: move lazily freed pages to inactive list

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Message-ID: <563A99A2.6010708@gmail.com>
Date:	Wed, 4 Nov 2015 18:49:54 -0500
From:	Daniel Micay <danielmicay@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-api@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	zhangyanfei@...fujitsu.com, Rik van Riel <riel@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jason Evans <je@...com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Michal Hocko <mhocko@...e.cz>, yalin.wang2010@...il.com,
	Shaohua Li <shli@...nel.org>,
	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Subject: Re: [PATCH 5/8] mm: move lazily freed pages to inactive list

> From a user perspective, it doesn't depend on swap. It's just slower
> without swap because it does what MADV_DONTNEED does. The current
> implementation can be dropped in where MADV_DONTNEED was previously used.

It just wouldn't replace existing layers of purging logic until that
edge case is fixed and it gains better THP integration.

It's already a very useful API with significant performance wins over
MADV_DONTNEED, so it will be useful. The only risk involved in landing
it is that a better feature might come along. Worst case scenario being
that the kernel ends up with a synonym for MADV_DONTNEED (but I think
there will still be a use case for this even if a pinning/unpinning API
existed, as this is more precise).

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