From mboxrd@z Thu Jan 1 00:00:00 1970 From: siarhei.siamashka@nokia.com (Siarhei Siamashka) Date: Thu, 29 Apr 2010 23:38:22 +0300 Subject: Can I use VFP in work queue context ? In-Reply-To: <13B9B4C6EF24D648824FF11BE896716203BABB88B0@dlee02.ent.ti.com> References: <2A1038AD87AFFA4291065666737B4EAA08CB0BA1BC@dlee06.ent.ti.com> <13B9B4C6EF24D648824FF11BE896716203BABB88B0@dlee02.ent.ti.com> Message-ID: <201004292338.22971.siarhei.siamashka@nokia.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. -- Best regards, Siarhei Siamashka