From: Borislav Petkov <bp@alien8.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <m.b.lankhorst@gmail.com>,
Borislav Petkov <bp@amd64.org>,
"Valdis.Kletnieks@vt.edu" <Valdis.Kletnieks@vt.edu>,
Ingo Molnar <mingo@elte.hu>, melwyn lobo <linux.melwyn@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: x86 memcpy performance
Date: Fri, 9 Sep 2011 17:35:53 +0200 [thread overview]
Message-ID: <20110909153553.GA12448@gere.osrc.amd.com> (raw)
In-Reply-To: <CA+55aFy5QOwQXqHkOkoMU_Lg6DrhrwVpMx4R0kFTnKqmACGy6w@mail.gmail.com>
On Fri, Sep 09, 2011 at 07:39:18AM -0700, Linus Torvalds wrote:
> Kernel memcpy's are basically almost always smaller than a page size,
> because that tends to be the fundamental allocation size.
Yeah, this is what my trace of a kernel build showed too:
Bytes Count
===== =====
...
224 3
225 3
227 3
244 1
254 5
255 13
256 21708
512 21746
848 12907
1920 36536
2048 21708
OTOH, I keep thinking that copy_*_user might be doing bigger sizes, for
example when shuffling network buffers to/from userspace. Converting
those to SSE memcpy might not be as easy as memcpy itself, though.
> Yes, there are exceptions that copy into big vmalloc'ed buffers, but
> they don't tend to matter. Things like module loading etc.
Too small a number of repetitions to matter, yes.
--
Regards/Gruss,
Boris.
next prev parent reply other threads:[~2011-09-09 15:36 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-12 17:59 melwyn lobo
2011-08-12 18:33 ` Andi Kleen
2011-08-12 19:52 ` Ingo Molnar
2011-08-14 9:59 ` Borislav Petkov
2011-08-14 11:13 ` Denys Vlasenko
2011-08-14 12:40 ` Borislav Petkov
2011-08-15 13:27 ` melwyn lobo
2011-08-15 13:44 ` Denys Vlasenko
2011-08-16 2:34 ` Valdis.Kletnieks
2011-08-16 12:16 ` Borislav Petkov
2011-09-01 15:15 ` Maarten Lankhorst
2011-09-01 16:18 ` Linus Torvalds
2011-09-08 8:35 ` Borislav Petkov
2011-09-08 10:58 ` Maarten Lankhorst
2011-09-09 8:14 ` Borislav Petkov
2011-09-09 10:12 ` Maarten Lankhorst
2011-09-09 11:23 ` Maarten Lankhorst
2011-09-09 13:42 ` Borislav Petkov
2011-09-09 14:39 ` Linus Torvalds
2011-09-09 15:35 ` Borislav Petkov [this message]
2011-12-05 12:20 ` melwyn lobo
2011-12-05 12:54 ` melwyn lobo
2011-12-05 14:36 ` Alan Cox
2011-08-15 14:55 Borislav Petkov
2011-08-15 14:59 ` Andy Lutomirski
2011-08-15 15:29 ` Borislav Petkov
2011-08-15 15:36 ` Andrew Lutomirski
2011-08-15 16:12 ` Borislav Petkov
2011-08-15 17:04 ` Andrew Lutomirski
2011-08-15 18:49 ` Borislav Petkov
2011-08-15 19:11 ` Andrew Lutomirski
2011-08-15 20:05 ` Borislav Petkov
2011-08-15 20:08 ` Andrew Lutomirski
2011-08-15 16:12 ` H. Peter Anvin
2011-08-15 16:58 ` Andrew Lutomirski
2011-08-15 18:26 ` H. Peter Anvin
2011-08-15 18:35 ` Andrew Lutomirski
2011-08-15 18:52 ` H. Peter Anvin
2011-08-16 7:19 ` melwyn lobo
2011-08-16 7:43 ` Borislav Petkov
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