From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Matt Sealey <matt@genesi-usa.com>
Cc: linuxppc-dev@ozlabs.org, Dominik Bozek <domino@mikroswiat.pl>,
Paul Mackerras <paulus@samba.org>,
linuxppc-embedded@ozlabs.org
Subject: Re: performance: memcpy vs. __copy_tofrom_user
Date: Sun, 12 Oct 2008 09:30:26 +1100 [thread overview]
Message-ID: <1223764226.8157.182.camel@pasglop> (raw)
In-Reply-To: <48EE2553.30903@genesi-usa.com>
On Thu, 2008-10-09 at 10:37 -0500, Matt Sealey wrote:
>
> Ahem, but nobody here wants AltiVec in the kernel do they?
It depends. We do use altivec in the kernel for example for
RAID accelerations.
The reason where we require a -real-good- reason to do it is
simply because of the drawbacks. The cost of enabling altivec
in the kernel can be high (especially if the user is using it)
and it's not context switched for kernel code (just like the
FPU) for obvious performance reasons. Thus any use of altivec in the
kernel must be done within non-preemptible sections, which can
cause higher latencies in preemptible kernels.
Ben.
next prev parent reply other threads:[~2008-10-11 22:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-08 14:39 performance: memcpy vs. __copy_tofrom_user Dominik Bozek
2008-10-08 15:31 ` Minh Tuan Duong
2008-10-08 15:39 ` Bill Gatliff
2008-10-08 15:42 ` Grant Likely
2008-10-09 2:34 ` Paul Mackerras
2008-10-09 10:12 ` Dominik Bozek
2008-10-09 11:06 ` Paul Mackerras
2008-10-09 11:41 ` Dominik Bozek
2008-10-09 12:04 ` Leon Woestenberg
2008-10-09 15:37 ` Matt Sealey
2008-10-11 22:30 ` Benjamin Herrenschmidt [this message]
2008-10-12 2:05 ` Matt Sealey
2008-10-12 4:05 ` Benjamin Herrenschmidt
2008-10-13 15:20 ` Scott Wood
2008-10-13 20:50 ` Benjamin Herrenschmidt
2008-10-13 21:03 ` Scott Wood
2008-10-14 2:14 ` Matt Sealey
2008-10-14 2:39 ` Benjamin Herrenschmidt
2008-10-14 15:10 ` Scott Wood
2008-10-15 1:37 ` Matt Sealey
2008-10-10 17:17 ` Dominik Bozek
2008-10-08 17:40 ` Scott Wood
2008-10-09 2:36 ` Paul Mackerras
2008-10-11 22:32 ` Benjamin Herrenschmidt
2008-10-13 15:06 ` Scott Wood
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