Date: Tue, 10 Apr 2012 16:05:13 -0400 From: Mike Meyer <mwm@mired.org> To: freebsd-hackers@freebsd.org Subject: Re: [RFT][patch] Scheduling for HTT and not only Message-ID: <20120410160513.0b322f68@bhuda.mired.org> In-Reply-To: <CACqU3MXo__hiKf%2Bs31c5WFZmVO_T8mJgu4A=KkMF=MWp8VoW4w@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> <4F7DE863.6080607@FreeBSD.org> <4F833F3D.7070106@FreeBSD.org> <CACqU3MXo__hiKf%2Bs31c5WFZmVO_T8mJgu4A=KkMF=MWp8VoW4w@mail.gmail.com>
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On Tue, 10 Apr 2012 12:58:00 -0400
Arnaud Lacombe <lacombar@gmail.com> wrote:
> Let me disagree on your conclusion. If OS A does a task in X seconds,
> and OS B does the same task in Y seconds, if Y > X, then OS B is just
> not performing good enough.
Others have pointed out one problem with this statement. Let me point
out another:
It ignores the purpose of the system. If you change the task to doing
N concurrent versions of the task, and OS A time increases linearly
with the number of tasks (say it's time X*N) but OS B stair-steps at
the number of processors in the system (i.e. Y*floor(N/P)), then OS A
is just not performing good enough.
A more concrete example: if OS B spends a couple of microseconds
optimizing disk access order and OS A doesn't, then a single process
writing to disk on OS A could well run faster than the same on OS
B. However, the maximum throughput on OS B as you add process will be
higher than it is on OS A. Which one you want will depend on what
you're using the system for.
<mike
--
Mike Meyer <mwm@mired.org> http://www.mired.org/
Independent Software developer/SCM consultant, email for more information.
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