Hans Petter Selasky wrote this message on Wed, May 13, 2015 at 10:35 +0200: > On 05/13/15 10:27, David Chisnall wrote: > > On 13 May 2015, at 09:03, John-Mark Gurney <jmg_at_funkthat.com> wrote: > >> > >> Poul-Henning Kamp wrote this message on Tue, May 12, 2015 at 06:31 +0000: > >>> -------- > >>> In message <20150512032307.GP37063_at_funkthat.com>, John-Mark Gurney writes: > >>> > >>>> Also, you'd probably see even better performance by increasing the > >>>> size to 64k, [...] > >>> > >>> easy: > >>> 8K on 32bit > >>> 64k on 64bit > >> > >> Sounds good to me... Just for people who care... I did a quick set of > >> benchmarks on sha256.. This is using my preliminary patch to use sse4 > >> optimized sha256... But this should be the same for others... > >> > >> The numbers in ministat output are the time in seconds it takes my > >> 3.4GHz AMD A10-5700 APU running HEAD to process a 512MB file, so lower > >> numbers are better.. I've processed them into easier to read format: > >> BUFSIZ: 145MB/sec > >> 8k: 193MB/sec > >> 16k: 198MB/sec > >> 64k: 202MB/sec > >> 128k: 202MB/sec > >> -t: 211MB/sec > > > > It looks like most of the benefit is gained at 16KB. Did you try running the benchmark with something else running at the same time to see if there is any advantage in trashing the caches a bit less (simple case, what happens if you run two instances of the same benchmark at once)? > > > > I suspect that you???re about right anyway - I recently did some tests while playing with JavaScript FFI generation with a multithreaded process JavaScript environment calling out to OpenSSL to do SHA calculations and having each of 8 threads reading in 128KB chunks gave the fastest performance (Core i7, 4 cores + hyperthreading), with only a negligible gain over 64KB. In all cases, the JavaScript implementation was significantly faster than the openssl tool, which used 8KB buffers. > > You should also try this using an USB disk. The performance numbers > heavily depends on the hardware's interrupt moderation values. This shouldn't matter.. I wasn't flushing the buffer cache between runs, so this was entirely from the buffer cache... This is purely, syscall+copy overhead that is being measured here... No matter what you're source is, NFS, USB disk, you'll always have this overhead... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."Received on Wed May 13 2015 - 16:02:26 UTC
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