Date: Sat, 7 Sep 2013 09:29:37 +0100 From: Andrew Turner <andrew@fubar.geek.nz> To: Warner Losh <imp@bsdimp.com> Cc: freebsd-arm@freebsd.org Subject: Re: stream benchmarking on RPi Message-ID: <20130907092937.0aee2245@bender.Home> In-Reply-To: <BB5295DB-7E79-4EE9-9056-577A4D270BE2@bsdimp.com> References: <CAHNYxxNtBcjD_Khq1_pYCMdPwZJmQ0M_GTmcaGWtoLOJkz_86g@mail.gmail.com> <BB5295DB-7E79-4EE9-9056-577A4D270BE2@bsdimp.com>
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On Thu, 5 Sep 2013 14:49:19 -0600 Warner Losh <imp@bsdimp.com> wrote: > > On Sep 5, 2013, at 2:02 PM, Jia-Shiun Li wrote: > > > Hi all, > > > > just did a brief test using stream, the memory bandwidth benchmark, > > on RPi with Raspbian and FreeBSD. Share these info to see if someone > > might think of it useful. > > > > FreeBSD is faster at copying. I guess that must be attributed to > > recent VM and/or superpage commits. I remembered it to be under > > 300MB/s months before. On the other hand, scale, add, and triad are > > significantly slower. Anyone have clues or any wild guesses? > > Soft float? This looks to be the case, stream uses floating point arithmetic for the scale, add, and triad tests. The copy test is a straight copy from one array of doubles to another. It looks like most of the speed up in the copy test is from the move from gcc to clang. I am planning on investigating moving to softfp on armv6 for 10.1. I don't expect this to cause any major issues as it is compatible with the current float ABI in that both pass floating point values in ARM registers. I think this will improve the test results, but may not be at the same level as Raspbian appears to use the hard-float ABI. This is also planned, however I am unsure when this will appear. Andrew
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