From: david mosberger <dmosberger@gmail.com>
To: linux-ia64@vger.kernel.org
Subject: Re: Change ia64 prefetch to use lfetch.fault
Date: Fri, 29 Jul 2005 01:58:36 +0000 [thread overview]
Message-ID: <ed5aea430507281858377ea50a@mail.gmail.com> (raw)
In-Reply-To: <200507282153.j6SLr0g01028@unix-os.sc.intel.com>
No, it doesn't --- it actually hurt performance last time I measured
it. Basically, Linux uses prefetch() too often with bad/NULL
pointers, IIRC. Check my earlier mails where I fixed the IVT code to
properly handle lfetch.fault (from a couple of months ago).
--david
On 7/28/05, Chen, Kenneth W <kenneth.w.chen@intel.com> wrote:
> I don't remember whether this has been discussed earlier, won't
> it make sense to use the fault variant of lfetch for prefetch()
> and prefetchw()? After all, the caller has high confidence that
> the cache line will be used in the future.
>
>
> Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
>
> --- linux-2.6.12/include/asm-ia64/processor.h.orig 2005-07-28 14:46:26.629519713 -0700
> +++ linux-2.6.12/include/asm-ia64/processor.h 2005-07-28 14:48:17.037721485 -0700
> @@ -682,13 +682,13 @@ ia64_imva (void *addr)
> static inline void
> prefetch (const void *x)
> {
> - ia64_lfetch(ia64_lfhint_none, x);
> + ia64_lfetch_fault(ia64_lfhint_none, x);
> }
>
> static inline void
> prefetchw (const void *x)
> {
> - ia64_lfetch_excl(ia64_lfhint_none, x);
> + ia64_lfetch_fault_excl(ia64_lfhint_none, x);
> }
>
> #define spin_lock_prefetch(x) prefetchw(x)
>
> -
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--
Mosberger Consulting LLC, voice/fax: 510-744-9372,
http://www.mosberger-consulting.com/
35706 Runckel Lane, Fremont, CA 94536
prev parent reply other threads:[~2005-07-29 1:58 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-28 21:53 Change ia64 prefetch to use lfetch.fault Chen, Kenneth W
2005-07-29 1:58 ` david mosberger [this message]
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