Messages in this thread |  | | | Date | Wed, 09 Sep 2009 01:53:48 +0300 | | From | Nikos Chantziaras <> | | Subject | Re: BFS vs. mainline scheduler benchmarks and measurements |
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On 09/08/2009 05:20 PM, Arjan van de Ven wrote: > On Tue, 08 Sep 2009 13:13:34 +0300 > Nikos Chantziaras<realnc@arcor.de> wrote: > >> On 09/08/2009 11:38 AM, Arjan van de Ven wrote: >>> On Tue, 08 Sep 2009 10:19:06 +0300 >>> Nikos Chantziaras<realnc@arcor.de> wrote: >>> >>>> latencytop has this to say: >>>> >>>> http://foss.math.aegean.gr/~realnc/pics/latop1.png >>>> >>>> Though I don't really understand what this tool is trying to tell >>>> me, I hope someone does. >>> >>> despite the untranslated content, it is clear that you have >>> scheduler delays (either due to scheduler bugs or cpu contention) >>> of upto 68 msecs... Second in line is your binary AMD graphics >>> driver that is chewing up 14% of your total latency... >> >> I've now used a correctly installed and up-to-date version of >> latencytop and repeated the test. Also, I got rid of AMD's binary >> blob and used kernel DRM drivers for my graphics card to throw fglrx >> out of the equation (which btw didn't help; the exact same problems >> occur). >> >> Here the result: >> >> http://foss.math.aegean.gr/~realnc/pics/latop2.png >> >> Again: this is on an Intel Core 2 Duo CPU. > > > so we finally have objective numbers! > > now the interesting part is also WHERE the latency hits. Because > fundamentally, if you oversubscribe the CPU, you WILL get scheduling > latency.. simply you have more to run than there is CPU.
Sounds plausible. However, with mainline this latency is very, very noticeable. With BFS I need to look really hard to detect it or do outright silly things, like a "make -j50". (At first I wrote "-j20" here but then went ahead an tested it just for kicks, and BFS would still let me use the GUI smoothly, LOL. So then I corrected it to "-j50"...)
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