On Fri, Sep 21, 2012 at 10:13:33AM +0100, Richard Davies wrote:

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.

Excellent!

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

Ok, so that is more or less acceptable. I would like to reduce the scanning
even further but I'll take this as a start -- largely because I do not have
any new good ideas on how it could be reduced further without incurring
a large cost in the page allocator :)

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

Were the boot times acceptable even when these slightly worse figures
were recorded?

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

Thank you!

Thank you for the detailed reporting and the testing, it's much
appreciated. I've already rebased the patches to Andrew's tree and tested
them overnight and the figures look good on my side. I'll update the
changelog and push them shortly.

-- 
Mel Gorman
SUSE Labs

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