From: Ingo Molnar <mingo@elte.hu>
To: Frederik Deweerdt <frederik.deweerdt@xprog.eu>
Cc: andi@firstfloor.org, tglx@linutronix.de, hpa@zytor.com,
linux-kernel@vger.kernel.org,
Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [patch] tlb flush_data: replace per_cpu with an array
Date: Mon, 12 Jan 2009 22:46:43 +0100 [thread overview]
Message-ID: <20090112214643.GD7320@elte.hu> (raw)
In-Reply-To: <20090112213539.GA10720@gambetta>
* Frederik Deweerdt <frederik.deweerdt@xprog.eu> wrote:
> Hi,
>
> On x86_64 flush tlb data is stored in per_cpu variables. This is
> unnecessary because only the first NUM_INVALIDATE_TLB_VECTORS entries
> are accessed.
>
> This patch aims at making the code less confusing (there's nothing
> really "per_cpu") by using a plain array. It also would save some memory
> on most distros out there (Ubuntu x86_64 has NR_CPUS=64 by default).
indeed, well spotted!
This construct was indeed an abuse of the per_cpu facilities.
Note that beyond the obvious memory savings, your patch should make the
code a bit faster and a bit smaller as well in the SMP TLB flush codepath:
the smp_flush_state data structure is 64 (or 128) bytes so static array
arithmetics will be faster than the per_cpu indirection.
I have applied your patch to tip/x86/mm, thanks Frederik!
Ingo
next prev parent reply other threads:[~2009-01-12 21:47 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-12 21:35 [patch] tlb flush_data: replace per_cpu with an array Frederik Deweerdt
2009-01-12 21:46 ` Ingo Molnar [this message]
2009-01-12 21:57 ` Andi Kleen
2009-01-12 22:10 ` Frederik Deweerdt
2009-01-12 22:32 ` Andi Kleen
2009-01-12 22:50 ` Ingo Molnar
2009-01-12 22:40 ` Ingo Molnar
2009-01-12 22:59 ` H. Peter Anvin
2009-01-13 2:43 ` Andi Kleen
2009-01-13 12:28 ` Ingo Molnar
2009-01-12 22:34 ` Ravikiran G Thirumalai
2009-01-12 23:00 ` Ingo Molnar
2009-01-12 23:09 ` Ingo Molnar
2009-01-13 2:14 ` Ravikiran G Thirumalai
2009-01-13 12:00 ` Peter Zijlstra
2009-01-13 12:33 ` Ingo Molnar
2009-01-13 18:13 ` Ravikiran G Thirumalai
2009-01-13 18:34 ` Ingo Molnar
2009-01-13 18:42 ` Ravikiran G Thirumalai
2009-01-14 7:31 ` Ingo Molnar
2009-01-15 7:15 ` Ravikiran G Thirumalai
2009-01-14 9:08 ` Andi Kleen
2009-01-14 14:41 ` Frederik Deweerdt
2009-01-14 15:20 ` Andi Kleen
2009-01-14 15:10 ` Frederik Deweerdt
2009-01-12 22:54 ` Mike Travis
2009-01-12 23:51 ` Frederik Deweerdt
2009-01-12 23:57 ` Mike Travis
2009-01-13 0:01 ` Ingo Molnar
2009-01-13 3:36 ` Andi Kleen
2009-01-13 12:14 ` Ingo Molnar
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