From: Scott Wood <scottwood@freescale•com>
To: benh@kernel•crashing.org
Cc: Dominik Bozek <domino@mikroswiat•pl>,
linuxppc-embedded@ozlabs•org, Paul Mackerras <paulus@samba•org>,
linuxppc-dev@ozlabs•org
Subject: Re: performance: memcpy vs. __copy_tofrom_user
Date: Mon, 13 Oct 2008 16:03:30 -0500 [thread overview]
Message-ID: <48F3B7A2.3010004@freescale.com> (raw)
In-Reply-To: <1223931027.8157.272.camel@pasglop>
Benjamin Herrenschmidt wrote:
>> It doesn't need to be done in non-preemptible sections, if you have a
>> separate per-thread save area for kernel fp/altivec use (and appropriate
>> flags so an FP unavailable handler knows which regs to restore), and you
>> can avoid using it in a preempting context.
>
> Yuck.
Hmm? It's simple and achieves the desired result (avoiding
non-preemptible regions without unduly restricting the ability to
extract performance from the hardware).
Would it be nicer to avoid FP/Altivec in the kernel altogether? Sure.
If the benchmarking says that we're better off with it, though, then so
be it.
-Scott
next prev parent reply other threads:[~2008-10-13 21:03 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
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 [this message]
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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