Can I use VFP in work queue context ?
siarhei.siamashka at nokia.com
Thu Apr 29 16:38:22 EDT 2010
On Thursday 22 April 2010 22:33:37 ext Woodruff, Richard wrote:
> > From: Nicolas Pitre [mailto:nico at fluxnic.net]
> > Sent: Thursday, April 22, 2010 12:20 PM
> > > If the work queue executes in a unique context it could follow the
> > > same lazy strategy a user space one does.
> > It could... but that begs the question: what is this that requires so
> > much processing power within the kernel? This really needs to be fully
> > understood and justified before even considering a possible VFP usage in
> > the kernel.
> A simple candidate is Neon memory copy. It can perform much better than the
> ARM based one. There are a few unfortunate copies associated with some
> networking devices which see decent benefit.
Yes, that was my intention from the start.
But after doing some benchmarks, now I suspect that the significant
performance improvement from using NEON instructions is specific to r1pX
Cortex-A8 revision in OMAP34xx/OMAP35xx and newer chips don't gain much.
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