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Date: Thu, 09 Aug 2012 08:18:38 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
CC: linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        Andi Kleen <ak@linux.intel.com>, Tim Chen <tim.c.chen@linux.intel.com>,
        Alex Shi <alex.shu@intel.com>, Jan Beulich <jbeulich@novell.com>,
        Robert Richter <robert.richter@amd.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Mel Gorman <mgorman@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH, RFC 0/6] Avoid cache trashing on clearing huge/gigantic
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On 07/20/2012 05:50 AM, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> Clearing a 2MB huge page will typically blow away several levels of CPU
> caches.  To avoid this only cache clear the 4K area around the fault
> address and use a cache avoiding clears for the rest of the 2MB area.
>
> It would be nice to test the patchset with more workloads. Especially if
> you see performance regression with THP.
>
> Any feedback is appreciated.
>
> Andi Kleen (6):
>    THP: Use real address for NUMA policy
>    mm: make clear_huge_page tolerate non aligned address
>    THP: Pass real, not rounded, address to clear_huge_page
>    x86: Add clear_page_nocache
>    mm: make clear_huge_page cache clear only around the fault address
>    x86: switch the 64bit uncached page clear to SSE/AVX v2
>

This is a mix of x86-specific and generic changes... does anyone mind if 
I put this into the -tip tree?

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.