From: Nick Piggin <npiggin@kernel.dk>
To: "Américo Wang" <xiyou.wangcong@gmail.com>
Cc: Nick Piggin <npiggin@gmail.com>,
"J. R. Okajima" <hooanon05@yahoo.co.jp>,
Nick Piggin <npiggin@kernel.dk>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: Big git diff speedup by avoiding x86 "fast string" memcmp
Date: Wed, 15 Dec 2010 16:54:50 +1100 [thread overview]
Message-ID: <20101215055450.GC3398@amd> (raw)
In-Reply-To: <20101215043840.GA7692@cr0.nay.redhat.com>
On Wed, Dec 15, 2010 at 12:38:40PM +0800, Américo Wang wrote:
> On Mon, Dec 13, 2010 at 07:25:05PM +1100, Nick Piggin wrote:
> >On Mon, Dec 13, 2010 at 6:29 PM, J. R. Okajima <hooanon05@yahoo.co.jp> wrote:
> >> But is the "rep cmp has quite a long latency" issue generic for all x86
> >> architecture, or Westmere system specific?
> >
> >I don't believe it is Westmere specific. Intel and AMD have
> >been improving these instructions in the past few years, so
> >Westmere is probably as good or better than any.
> >
> >That said, rep cmp may not be as heavily optimized as the
> >set and copy string instructions.
> >
> >In short, I think the change should be suitable for all x86 CPUs,
> >but I would like to hear more opinions or see numbers for other
> >cores.
> >
>
> How about other arch? If this is only for x86, shouldn't it be
> protected by CONFIG_X86?
That's what I would like to know, but I suspect that for very short
strings we are dealing with, the custom loop will be fine for
everybody.
next prev parent reply other threads:[~2010-12-15 5:55 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-09 7:09 Big git diff speedup by avoiding x86 "fast string" memcmp Nick Piggin
2010-12-09 13:37 ` Borislav Petkov
2010-12-10 2:38 ` Nick Piggin
2010-12-10 2:38 ` Nick Piggin
2010-12-10 2:38 ` Nick Piggin
2010-12-10 4:27 ` Nick Piggin
2010-12-10 14:23 ` J. R. Okajima
2010-12-13 1:45 ` Nick Piggin
2010-12-13 7:29 ` J. R. Okajima
2010-12-13 8:25 ` Nick Piggin
2010-12-14 19:01 ` J. R. Okajima
2010-12-15 4:06 ` Nick Piggin
2010-12-15 5:57 ` J. R. Okajima
2010-12-15 13:15 ` Boaz Harrosh
2010-12-15 18:00 ` David Miller
2010-12-16 9:53 ` Boaz Harrosh
2010-12-16 13:13 ` Nick Piggin
2010-12-16 14:03 ` Boaz Harrosh
2010-12-16 14:15 ` Nick Piggin
2010-12-16 16:51 ` Linus Torvalds
2010-12-16 17:57 ` David Miller
2010-12-15 4:38 ` Américo Wang
2010-12-15 5:54 ` Nick Piggin [this message]
2010-12-15 7:12 ` Linus Torvalds
2010-12-15 23:09 ` Tony Luck
2010-12-16 2:34 ` Nick Piggin
-- strict thread matches above, loose matches on Subject: below --
2010-12-18 22:54 George Spelvin
2010-12-19 14:28 ` Boaz Harrosh
2010-12-19 15:46 ` Nick Piggin
2010-12-19 17:06 ` George Spelvin
2010-12-21 9:26 ` Nick Piggin
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