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Date: Fri, 21 Sep 2012 10:13:33 +0100
From: Richard Davies <richard@arachsys.com>
Subject: Re: [PATCH 0/6] Reduce compaction scanning and lock contention
Message-ID: <20120921091333.GA32081@alpha.arachsys.com>
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To: Mel Gorman <mgorman@suse.de>
Cc: Shaohua Li <shli@kernel.org>, Rik van Riel <riel@redhat.com>, Avi Kivity <avi@redhat.com>, QEMU-devel <qemu-devel@nongnu.org>, KVM <kvm@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>

Hi Mel,

Thank you for this series. I have applied on clean 3.6-rc5 and tested, and
it works well for me - the lock contention is (still) gone and
isolate_freepages_block is much reduced.

Here is a typical test with these patches:

# grep -F '[k]' report | head -8
    65.20%         qemu-kvm  [kernel.kallsyms]     [k] clear_page_c
     2.18%         qemu-kvm  [kernel.kallsyms]     [k] isolate_freepages_block
     1.56%         qemu-kvm  [kernel.kallsyms]     [k] _raw_spin_lock
     1.40%         qemu-kvm  [kernel.kallsyms]     [k] svm_vcpu_run
     1.38%          swapper  [kernel.kallsyms]     [k] default_idle
     1.35%         qemu-kvm  [kernel.kallsyms]     [k] get_page_from_freelist
     0.74%             ksmd  [kernel.kallsyms]     [k] memcmp
     0.72%         qemu-kvm  [kernel.kallsyms]     [k] free_pages_prepare


I did manage to get a couple which were slightly worse, but nothing like as
bad as before. Here are the results:

# grep -F '[k]' report | head -8
    45.60%       qemu-kvm  [kernel.kallsyms]     [k] clear_page_c
    11.26%       qemu-kvm  [kernel.kallsyms]     [k] isolate_freepages_block
     3.21%       qemu-kvm  [kernel.kallsyms]     [k] _raw_spin_lock
     2.27%           ksmd  [kernel.kallsyms]     [k] memcmp
     2.02%        swapper  [kernel.kallsyms]     [k] default_idle
     1.58%       qemu-kvm  [kernel.kallsyms]     [k] svm_vcpu_run
     1.30%       qemu-kvm  [kernel.kallsyms]     [k] _raw_spin_lock_irqsave
     1.09%       qemu-kvm  [kernel.kallsyms]     [k] get_page_from_freelist

# grep -F '[k]' report | head -8
    61.29%       qemu-kvm  [kernel.kallsyms]     [k] clear_page_c
     4.52%       qemu-kvm  [kernel.kallsyms]     [k] _raw_spin_lock_irqsave
     2.64%       qemu-kvm  [kernel.kallsyms]     [k] copy_page_c
     1.61%        swapper  [kernel.kallsyms]     [k] default_idle
     1.57%       qemu-kvm  [kernel.kallsyms]     [k] _raw_spin_lock
     1.18%       qemu-kvm  [kernel.kallsyms]     [k] get_page_from_freelist
     1.18%       qemu-kvm  [kernel.kallsyms]     [k] isolate_freepages_block
     1.11%       qemu-kvm  [kernel.kallsyms]     [k] svm_vcpu_run

I will follow up with the detailed traces for these three tests.

Thank you!

Richard.

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