linux-kernel - Re: REGRESSION: Performance regressions from switching anon

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Message-ID: <87ea4bd7-8b16-4b24-8fcb-d8e9b6f421ec@email.android.com>
Date:	Wed, 15 Jun 2011 14:51:34 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Tim Chen <tim.c.chen@...ux.intel.com>
CC:	Andi Kleen <ak@...ux.intel.com>, Shaohua Li <shaohua.li@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Russell King <rmk@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	"Luck, Tony" <tony.luck@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
	Namhyung Kim <namhyung@...il.com>,
	"Shi, Alex" <alex.shi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex



Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>removing
>that sysconf() wreckage closed the gap considerably (needing to know
>the
>number of cpus to optimize locking sounds like a trainwreck all of its
>own, needing it _that_ often instead of just once at startup is even
>worse).

Yeah, I think it's ridiculous to say that glibc is not doing something stupid and that it's a problem with kernel interfaces.

Do the proc file parsing once and cache the result in a static variable. Doing it over and over again is just crazy.

Adding new system calls because glibc is crazy is insane.

       Linus

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