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From: Rusty Russell <rusty@rustcorp.com.au>
To: Tejun Heo <tj@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Christoph Lameter <cl@linux-foundation.org>,
	Ingo Molnar <mingo@elte.hu>,
	travis@sgi.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	steiner@sgi.com, Hugh Dickins <hugh@veritas.com>
Subject: Re: regarding the x86_64 zero-based percpu patches
Date: Thu, 15 Jan 2009 12:17:53 +1030	[thread overview]
Message-ID: <200901151217.54989.rusty@rustcorp.com.au> (raw)
In-Reply-To: <496D6300.9070402@kernel.org>

On Wednesday 14 January 2009 14:28:56 Tejun Heo wrote:
> The main problem is that the area needs to be congruent which
> basically mandates them to be contiguous.

I want to explore this assumption a little.  Logically, yes, if 50% of pages are free and we have 4096 cpus, the chance that a page is free on all CPUs is 1 in 2^4095.  But maybe such systems are fine with 2M pages for per-cpu areas at boot?  And can page mobility tricks help us make the odds reasonable here?
Only allowing movable pages in our expansion-of-percpu area?

Thanks,
Rusty.

  reply	other threads:[~2009-01-15  3:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <49649814.4040005@kernel.org>
     [not found] ` <20090107120225.GA30651@elte.hu>
2009-01-07 12:13   ` regarding the x86_64 zero-based percpu patches Tejun Heo
2009-01-10  6:46     ` Rusty Russell
2009-01-12 17:23       ` Christoph Lameter
2009-01-12 17:44         ` Eric W. Biederman
2009-01-12 19:00           ` Christoph Lameter
2009-01-13  0:33           ` Tejun Heo
2009-01-13  3:01             ` Eric W. Biederman
2009-01-13  3:14               ` Tejun Heo
2009-01-13  4:07                 ` Eric W. Biederman
2009-01-14  3:58                   ` Tejun Heo
2009-01-15  1:47                     ` Rusty Russell [this message]
2009-01-15  1:49                   ` Rusty Russell
2009-01-15 20:26                     ` Christoph Lameter
2009-01-15  1:34           ` Rusty Russell
2009-01-15 13:55             ` Ingo Molnar
2009-01-15 20:27             ` Christoph Lameter

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