From: Alex Shi <alex.shi@intel.com>
To: "H. Peter Anvin" <hpa@zytor.com>,
cl@linux-foundation.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
mgorman@suse.de, Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-mm@vger.kernel.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: unnecessary tlb flush in mprotect
Date: Tue, 22 May 2012 09:08:47 +0800 [thread overview]
Message-ID: <4FBAE71F.5000801@intel.com> (raw)
In-Reply-To: <4FB9FD1D.6000001@intel.com>
On 05/21/2012 04:30 PM, Alex Shi wrote:
> when mprotect just change prots of non-present pages, current mprotect
> still do the tlb flush in check_protection().
> but according to 4.10.2.3 Intel SDM V3A (
> www.intel.com/Assets/ja_JP/PDF/manual/253668.pdf ) at that time, TLB has
> no this lines for this page. So, tlb flush is just waste time. (for cr3
> rewrite, flush all tlb, or invlpg, like a 'nop' in intel cpu)
>
> Do we need to add the pte_present similar check here to prevent the
> unnecessary tlb flushing? I mean, are there real case in word, User like
> to change page prots before assign a physical page to it?
>
Any comments from linux-mm emailing list?
>
>
> Alex Shi
next prev parent reply other threads:[~2012-05-22 1:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-21 8:30 unnecessary tlb flush in mprotect Alex Shi
2012-05-22 1:08 ` Alex Shi [this message]
2012-05-22 16:37 ` Andi Kleen
2012-05-23 0:06 ` Alex Shi
2012-05-26 18:46 ` Hugh Dickins
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