linux-kernel - Re: pthread_create() slow for many threads; also time to revisit 64b context switch optimization?

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Date:	Wed, 13 Aug 2008 11:22:39 -0700
From:	Ulrich Drepper <drepper@...hat.com>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	hugh@...itas.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	briangrant@...gle.com, cgd@...gle.com, mbligh@...gle.com,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: pthread_create() slow for many threads; also time to revisit
 64b context switch optimization?

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Arjan van de Ven wrote:
> yeah maybe we should also tell it we expect it to be used downwards.
> Oh wait.. MAP_GROWSDOWN ?

MAP_GROWSDOWN is unusable because we have to allocate the entire address
range for the stack.  Otherwise some other allocation happens in that
range and all of a sudden the stack cannot grow as much as needed anymore.

These flags really can be removed.  They should not be used because they
are outright dangerous.

- --
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
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