Messages in this thread |  | | Date | Wed, 18 Oct 2000 19:25:12 +0200 | From | Markus Pfeiffer <> | Subject | Re: Processor affinity planned for 2.5? |
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Wasnt my idea ... I´ll forward this to the guy who asked ... On 128 CPU machines affinity to processor groups may be a thing to consider but not on 2 or 4 way SMPs ...
Anyway, I appreciate that he asked on linux-SMP and not here ... less traffic in here ...
Markus
Jakob Østergaard wrote: > > On Wed, Oct 18, 2000 at 01:13:48PM +0200, Markus Pfeiffer wrote: > > HI all > > > > I received and discussed Processor-affinity on the SMP-Kernel-list and I > > only wanted to ask if there is something in preparation or if someone > > (especially Linus :)) is against this ... I was asked this question > > beacause someone wanted to do some Matrix-Operations on his SMP machine > > and wnated to speed them up by trying affinity ... > > I don't know the exact answer to your question, but I can tell you that there > has been patches floating around for a long time (somehwere) to provide > processor affinity for processes in the Linux kernel. > > However, the patches has never been merged because: > *) No matter how self-contained and simple and elegant they may be, > they complicate the scheduler (maybe not much, but more than not) > *) There is no performance gain what so ever, expcept for perhaps some > very specially fabricated benchmark in some very specially fabricated > test environment. In the best case, you will not get a slowdown from > the explicit affinity. > > Think about it: It's the scheduler's job to distribute the threads of > execution reasonably among the available processors. The scheduler knows the > state of the system and *you* don't when you put in your static affinity > decisions. You are bound to lose. > > Yes, I know that big-iron IRIX boxes have explicit processor affinity available > to user-space. They also have gang-scheduling, which is more complicated and > maybe more likely to actually give you a speedup than explicit affinity. IRIX > has a lot of things, and let's not get into *that* one again ;) > > If you want to achieve anything in life, keep it simple. Be happy you have a > scheduler that on any day can do a better job than you at scheduling the > threads, and get on with your work :) > > Cheers, > -- > ................................................................ > : jakob@unthought.net : And I see the elder races, : > :.........................: putrid forms of man : > : Jakob Østergaard : See him rise and claim the earth, : > : OZ9ABN : his downfall is at hand. : > :.........................:............{Konkhra}...............: > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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