linux-kernel - Re: [PATCH] mm: raise MemFree by reverting percpu_pagelist

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Message-ID: <CA+55aFztbcB1sULup-rCsWmOaC7RFLvuJ=sqGQz=SAKzys02mw@mail.gmail.com>
Date:	Fri, 11 May 2012 09:54:18 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Minchan Kim <minchan@...nel.org>, Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: raise MemFree by reverting percpu_pagelist_fraction
 to 0

On Fri, May 11, 2012 at 9:35 AM, Sasha Levin <levinsasha928@...il.com> wrote:
>
> Once it's on, we reserve 1/x of the pages for the pagelists. I'm not
> sure why 8 was selected in the first place, but I guess it made sense
> that you don't want to reserve 15%+ of your memory for the pagelists.

Why not just accept any number, but turn small numbers into the minimum?

And if it's a per-cpu, then the minimum had better depend on number of
CPU's anyway. 15% of memory on a single-cpu already sounds insanely
high, but if you have several cpu's, it's going to be just totally
crazy.

So a minimum of 8 already sounds broken. Exposing that minimum in a
way that makes it impossible to reset it sounds just insane.

                    Linus
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