From: Borislav Petkov <bp@alien8.de>
To: Andrew Lutomirski <luto@mit.edu>
Cc: melwyn lobo <linux.melwyn@gmail.com>,
Denys Vlasenko <vda.linux@googlemail.com>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
borislav.petkov@amd.com
Subject: Re: x86 memcpy performance
Date: Mon, 15 Aug 2011 22:05:10 +0200 [thread overview]
Message-ID: <20110815200510.GA10141@liondog.tnic> (raw)
In-Reply-To: <CAObL_7HPssPSaMMKdc-9LFKQXUnreFxMy4g8g2b7KdiRkBPW7w@mail.gmail.com>
On Mon, Aug 15, 2011 at 03:11:40PM -0400, Andrew Lutomirski wrote:
> > Well, copy_from_user... does a bunch of rep; movsq - if the SSE version
> > shows reasonable speedup there, we might need to make those work too.
>
> I'm a little surprised that SSE beats fast string operations, but I
> guess benchmarking always wins.
If by fast string operations you mean X86_FEATURE_ERMS, then that's
Intel-only and that actually would need to be benchmarked separately.
Currently, I see speedup for large(r) buffers only vs rep; movsq. But I
dunno about rep; movsb's enhanced rep string tricks Intel does.
> Yes. But we don't nest that much, and the save/restore isn't all that
> expensive. And we don't have to save/restore unless kernel entries
> nest and both entries try to use kernel_fpu_begin at the same time.
Yep.
> This whole project may take awhile. The code in there is a
> poorly-documented mess, even after Hans' cleanups. (It's a lot worse
> without them, though.)
Oh yeah, this code could use lotsa scrubbing :)
--
Regards/Gruss,
Boris.
next prev parent reply other threads:[~2011-08-15 20:05 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-15 14:55 x86 memcpy performance 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 [this message]
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
-- strict thread matches above, loose matches on Subject: below --
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
2011-12-05 12:20 ` melwyn lobo
2011-12-05 12:54 ` melwyn lobo
2011-12-05 14:36 ` Alan Cox
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