From: "J. R. Okajima" <hooanon05@yahoo.co.jp>
To: Nick Piggin <npiggin@kernel.dk>
Cc: 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: Mon, 13 Dec 2010 16:29:11 +0900 [thread overview]
Message-ID: <9580.1292225351@jrobl> (raw)
In-Reply-To: <20101213014553.GA6522@amd>
Nick Piggin:
> It's not scaling but just single threaded performance. gcc turns memcmp
> into rep cmp, which has quite a long latency, so it's not appripriate
> for short strings.
Honestly speaking I doubt how this 'long *' approach is effective
(Of course it never means that your result (by 'char *') is doubtful).
But is the "rep cmp has quite a long latency" issue generic for all x86
architecture, or Westmere system specific?
J. R. Okajima
next prev parent reply other threads:[~2010-12-13 7:37 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 [this message]
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
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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