linux-kernel - Re: [PATCH v2 1/3] deactivate invalidated pages

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Message-Id: <20101129110848.82A8.A69D9226@jp.fujitsu.com>
Date:	Mon, 29 Nov 2010 11:13:53 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Ben Gamari <bgamari.foss@...il.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH v2 1/3] deactivate invalidated pages

> > I don't like this change because fadvise(DONT_NEED) is rarely used
> > function and this PG_reclaim trick doesn't improve so much. In the
> > other hand, It increase VM state mess.
> > 
> 
> Can we please stop appealing to this argument? The reason that
> fadvise(DONT_NEED) is currently rarely employed is that the interface as
> implemented now is extremely kludgey to use.
> 
> Are you proposing that this particular implementation is not worth the
> mess (as opposed to putting the pages at the head of the inactive list
> as done earlier) or would you rather that we simply leave DONT_NEED in
> its current state? Even if today's gains aren't as great as we would
> like them to be, we should still make an effort to make fadvise()
> usable, if for no other reason than to encourage use in user-space so
> that applications can benefit when we finally do figure out how to
> properly account for the user's hints.

Hi

I'm not againt DONT_NEED feature. I only said PG_reclaim trick is not
so effective. Every feature has their own pros/cons. I think the cons
is too big. Also, nobody have mesured PG_reclaim performance gain. Did you?



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