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Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur

To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 20 Mar 2015 11:23:11 +1100
Cc: Mel Gorman <mgorman@xxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Aneesh Kumar <aneesh.kumar@xxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Linux-MM <linux-mm@xxxxxxxxx>, xfs@xxxxxxxxxxx, ppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>
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References: <20150317070655.GB10105@dastard> <CA+55aFzdLnFdku-gnm3mGbeS=QauYBNkFQKYXJAGkrMd2jKXhw@xxxxxxxxxxxxxx> <20150317205104.GA28621@dastard> <CA+55aFzSPcNgxw4GC7aAV1r0P5LniyVVC66COz=3cgMcx73Nag@xxxxxxxxxxxxxx> <20150317220840.GC28621@dastard> <CA+55aFwne-fe_Gg-_GTUo+iOAbbNpLBa264JqSFkH79EULyAqw@xxxxxxxxxxxxxx> <CA+55aFy-Mw74rAdLMMMUgnsG3ZttMWVNGz7CXZJY7q9fqyRYfg@xxxxxxxxxxxxxx> <CA+55aFyxA9u2cVzV+S7TSY9ZvRXCX=z22YAbi9mdPVBKmqgR5g@xxxxxxxxxxxxxx> <20150319224143.GI10105@dastard> <CA+55aFy5UeNnFUTi619cs3b9Up2NQ1wbuyvcCS614+o3=z=wBQ@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Mar 19, 2015 at 04:05:46PM -0700, Linus Torvalds wrote:
> Can you try Mel's change to make it use
> 
>         if (!(vma->vm_flags & VM_WRITE))
> 
> instead of the pte details? Again, on otherwise plain 3.19, just so
> that we have a baseline. I'd be *so* much happer with checking the vma
> details over per-pte details, especially ones that change over the
> lifetime of the pte entry, and the NUMA code explicitly mucks with.

$ sudo perf_3.18 stat -a -r 6 -e migrate:mm_migrate_pages sleep 10

 Performance counter stats for 'system wide' (6 runs):

    266,750      migrate:mm_migrate_pages ( +-  7.43% )

          10.002032292 seconds time elapsed ( +-  0.00% )

Bit more variance there than the pte checking, but runtime
difference is in the noise - 5m4s vs 4m54s - and profiles are
identical to the pte checking version.

Cheers,

Dave.

-- 
Dave Chinner
david@xxxxxxxxxxxxx

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