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    SubjectRE: [PATCH RFC] [x86] Optimize copy-page by reducing impact from HW prefetch
    Sure, I separate two patches ASAP, one is for performance tuning code after some experiments,
    another code style patch.

    Thanks
    Ling

    > -----Original Message-----
    > From: Ingo Molnar [mailto:mingo@elte.hu]
    > Sent: Thursday, June 23, 2011 3:05 PM
    > To: Andi Kleen
    > Cc: Ma, Ling; hpa@zytor.com; tglx@linutronix.de; linux-
    > kernel@vger.kernel.org
    > Subject: Re: [PATCH RFC] [x86] Optimize copy-page by reducing impact
    > from HW prefetch
    >
    >
    > * Andi Kleen <andi@firstfloor.org> wrote:
    >
    > > ling.ma@intel.com writes:
    > >
    > > > impact(DCU prefetcher), and simplify original code. The
    > > > performance is improved about 15% on core2, 36% on snb
    > > > respectively. (We use our micro-benchmark, and will do further
    > > > test according to your requirment)
    > >
    > > This doesn't make a lot of sense because neither Core-2 nor SNB use
    > > the code path you patched. They all use the rep ; movs path
    >
    > Ling, mind double checking which one is the faster/better one on SNB,
    > in cold-cache and hot-cache situations, copy_page or copy_page_c?
    >
    > Also, while looking at this file please fix the countless pieces of
    > style excrements it has before modifying it:
    >
    > - non-Linux comment style (and needless two comments - it can
    > be in one comment block):
    >
    > /* Don't use streaming store because it's better when the target
    > ends up in cache. */
    >
    > /* Could vary the prefetch distance based on SMP/UP */
    >
    > - (there's other non-standard comment blocks in this file as well)
    >
    > - The copy_page/copy_page_c naming is needlessly obfuscated, it
    > should be copy_page, copy_page_norep or so - the _c postfix has no
    > obvious meaning.
    >
    > - all #include's should be at the top
    >
    > - please standardize it on the 'instrn %x, %y' pattern that we
    > generally use in arch/x86/, not 'instrn %x,%y' pattern.
    >
    > and do this cleanup patch first and the speedup on top of it, and
    > keep the two in two separate patches so that the modification to the
    > assembly code can be reviewed more easily.
    >
    > Thanks,
    >
    > Ingo


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