Date: Fri, 6 Apr 2012 15:13:18 +0100 From: Attilio Rao <attilio@freebsd.org> To: Arnaud Lacombe <lacombar@gmail.com> Cc: Florian Smeets <flo@freebsd.org>, freebsd-hackers@freebsd.org, Alexander Motin <mav@freebsd.org>, Andriy Gapon <avg@freebsd.org>, FreeBSD current <freebsd-current@freebsd.org>, Jeff Roberson <jroberson@jroberson.net> Subject: Re: [RFT][patch] Scheduling for HTT and not only Message-ID: <CAJ-FndC7FTcry2N=F4==K_vBvekOiR647Ng5aY8VU4K0EojSvg@mail.gmail.com> In-Reply-To: <CACqU3MWZj503xN_-wr6s%2BXOB7JGhhBgaWW0gOX60KJvU3Y=Rig@mail.gmail.com> References: <4F2F7B7F.40508@FreeBSD.org> <4F366E8F.9060207@FreeBSD.org> <4F367965.6000602@FreeBSD.org> <4F396B24.5090602@FreeBSD.org> <alpine.BSF.2.00.1202131012270.2020@desktop> <4F3978BC.6090608@FreeBSD.org> <alpine.BSF.2.00.1202131108460.2020@desktop> <4F3990EA.1080002@FreeBSD.org> <4F3C0BB9.6050101@FreeBSD.org> <alpine.BSF.2.00.1202150949480.2020@desktop> <4F3E807A.60103@FreeBSD.org> <CACqU3MWEC4YYguPQF_d%2B_i_CwTc=86hG%2BPbxFgJQiUS-=AHiRw@mail.gmail.com> <4F3E8858.4000001@FreeBSD.org> <CACqU3MWZj503xN_-wr6s%2BXOB7JGhhBgaWW0gOX60KJvU3Y=Rig@mail.gmail.com>
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Il 05 aprile 2012 19:12, Arnaud Lacombe <lacombar@gmail.com> ha scritto: > Hi, > > [Sorry for the delay, I got a bit sidetrack'ed...] > > 2012/2/17 Alexander Motin <mav@freebsd.org>: >> On 17.02.2012 18:53, Arnaud Lacombe wrote: >>> >>> On Fri, Feb 17, 2012 at 11:29 AM, Alexander Motin<mav@freebsd.org> =C2= =A0wrote: >>>> >>>> On 02/15/12 21:54, Jeff Roberson wrote: >>>>> >>>>> On Wed, 15 Feb 2012, Alexander Motin wrote: >>>>>> >>>>>> I've decided to stop those cache black magic practices and focus on >>>>>> things that really exist in this world -- SMT and CPU load. I've >>>>>> dropped most of cache related things from the patch and made the res= t >>>>>> of things more strict and predictable: >>>>>> http://people.freebsd.org/~mav/sched.htt34.patch >>>>> >>>>> >>>>> This looks great. I think there is value in considering the other >>>>> approach further but I would like to do this part first. It would be >>>>> nice to also add priority as a greater influence in the load balancin= g >>>>> as well. >>>> >>>> >>>> I haven't got good idea yet about balancing priorities, but I've >>>> rewritten >>>> balancer itself. As soon as sched_lowest() / sched_highest() are more >>>> intelligent now, they allowed to remove topology traversing from the >>>> balancer itself. That should fix double-swapping problem, allow to kee= p >>>> some >>>> affinity while moving threads and make balancing more fair. I did numb= er >>>> of >>>> tests running 4, 8, 9 and 16 CPU-bound threads on 8 CPUs. With 4, 8 an= d >>>> 16 >>>> threads everything is stationary as it should. With 9 threads I see >>>> regular >>>> and random load move between all 8 CPUs. Measurements on 5 minutes run >>>> show >>>> deviation of only about 5 seconds. It is the same deviation as I see >>>> caused >>>> by only scheduling of 16 threads on 8 cores without any balancing need= ed >>>> at >>>> all. So I believe this code works as it should. >>>> >>>> Here is the patch: http://people.freebsd.org/~mav/sched.htt40.patch >>>> >>>> I plan this to be a final patch of this series (more to come :)) and i= f >>>> there will be no problems or objections, I am going to commit it (exce= pt >>>> some debugging KTRs) in about ten days. So now it's a good time for >>>> reviews >>>> and testing. :) >>>> >>> is there a place where all the patches are available ? >> >> >> All my scheduler patches are cumulative, so all you need is only the las= t >> mentioned here sched.htt40.patch. >> > You may want to have a look to the result I collected in the > `runs/freebsd-experiments' branch of: > > https://github.com/lacombar/hackbench/ > > and compare them with vanilla FreeBSD 9.0 and -CURRENT results > available in `runs/freebsd'. On the dual package platform, your patch > is not a definite win. > >> But in some cases, especially for multi-socket systems, to let it show i= ts >> best, you may want to apply additional patch from avg@ to better detect = CPU >> topology: >> https://gitorious.org/~avg/freebsd/avgbsd/commit/6bca4a2e4854ea3fc275946= a023db65c483cb9dd >> > test I conducted specifically for this patch did not showed much improvem= ent... Can you please clarify on this point? The test you did included cases where the topology was detected badly against cases where the topology was detected correctly as a patched kernel (and you still didn't see a performance improvement), in terms of cache line sharing? Attilio --=20 Peace can only be achieved by understanding - A. Einstein
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