From: "H. Peter Anvin" <hpa@zytor.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>,
David Miller <davem@davemloft.net>,
torvalds@linux-foundation.org, mingo@elte.hu,
nickpiggin@yahoo.com.au, sqazi@google.com,
linux-kernel@vger.kernel.org, tglx@linutronix.de
Subject: Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()
Date: Sat, 28 Feb 2009 17:40:51 -0800 [thread overview]
Message-ID: <49A9E7A3.4050102@zytor.com> (raw)
In-Reply-To: <20090228173813.6d86c0ef@infradead.org>
Arjan van de Ven wrote:
>
> the reason that movntq and co are faster is because you avoid the
> write-allocate behavior of the caches....
>
> the cache polluting part of it I find hard to buy for general use (as
> this discussion shows)... that will be extremely hard to measure as
> a real huge thing, while the WA part is like a 1.5x to 2x thing.
>
Note that hardware *can* (which is not the same thing as hardware
*will*) elide the write-allocate behavior. We did that at Transmeta for
rep movs and certain other instructions which provably filled in entire
cache lines. I haven't investigated if newer Intel CPUs do that in the
"fast rep movs" case.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-03-01 1:44 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-24 2:03 Performance regression in write() syscall Salman Qazi
2009-02-24 4:10 ` Nick Piggin
2009-02-24 4:28 ` Linus Torvalds
2009-02-24 9:02 ` Nick Piggin
2009-02-24 15:52 ` Linus Torvalds
2009-02-24 16:24 ` Andi Kleen
2009-02-24 16:51 ` Ingo Molnar
2009-02-25 3:23 ` Nick Piggin
2009-02-25 7:25 ` [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache() Ingo Molnar
2009-02-25 8:09 ` Nick Piggin
2009-02-25 8:29 ` Ingo Molnar
2009-02-25 8:59 ` Nick Piggin
2009-02-25 12:01 ` Ingo Molnar
2009-02-25 16:04 ` Linus Torvalds
2009-02-25 16:29 ` Ingo Molnar
2009-02-27 12:05 ` Nick Piggin
2009-02-28 8:29 ` Ingo Molnar
2009-02-28 11:49 ` Nick Piggin
2009-02-28 12:58 ` Ingo Molnar
2009-02-28 17:16 ` Linus Torvalds
2009-02-28 17:24 ` Arjan van de Ven
2009-02-28 17:42 ` Linus Torvalds
2009-02-28 17:53 ` Arjan van de Ven
2009-02-28 18:05 ` Andi Kleen
2009-02-28 18:27 ` Ingo Molnar
2009-02-28 18:39 ` Arjan van de Ven
2009-03-02 10:39 ` [PATCH] x86, mm: dont use non-temporal stores in pagecache accesses Ingo Molnar
2009-02-28 18:52 ` [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache() Linus Torvalds
2009-03-01 14:19 ` Nick Piggin
2009-03-01 0:06 ` David Miller
2009-03-01 0:40 ` Andi Kleen
2009-03-01 0:28 ` H. Peter Anvin
2009-03-01 0:38 ` Arjan van de Ven
2009-03-01 1:48 ` Andi Kleen
2009-03-01 1:38 ` Arjan van de Ven
2009-03-01 1:40 ` H. Peter Anvin [this message]
2009-03-01 14:06 ` Nick Piggin
2009-03-02 4:46 ` H. Peter Anvin
2009-03-02 6:18 ` Nick Piggin
2009-03-02 21:16 ` Linus Torvalds
2009-03-02 21:25 ` Ingo Molnar
2009-03-03 4:30 ` Nick Piggin
2009-03-03 4:20 ` Nick Piggin
2009-03-03 9:02 ` Ingo Molnar
2009-03-04 3:37 ` Nick Piggin
2009-03-01 2:07 ` Andi Kleen
2009-02-24 5:43 ` Performance regression in write() syscall Salman Qazi
2009-02-24 10:09 ` Andi Kleen
2009-02-24 16:13 ` Ingo Molnar
2009-02-24 16:51 ` Andi Kleen
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