Date: Sun, 13 Sep 2015 16:44:40 +0300 From: Dmitry Sivachenko <trtrmitya@gmail.com> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: FreeBSD Stable ML <stable@freebsd.org> Subject: Re: process scheduling and cpuset Message-ID: <C6ADA4B7-1126-44A5-94B3-97FA79C8582A@gmail.com> In-Reply-To: <20150913130920.GR3158@zxy.spb.ru> References: <623FA99E-04E7-4D29-953A-61EE7B35CBF6@gmail.com> <20150913130920.GR3158@zxy.spb.ru>
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> On 13 =D1=81=D0=B5=D0=BD=D1=82. 2015 =D0=B3., at 16:09, Slawa = Olhovchenkov <slw@zxy.spb.ru> wrote: >=20 > On Sun, Sep 13, 2015 at 02:52:08PM +0300, Dmitry Sivachenko wrote: >=20 >> Hello, >>=20 >> I have 32 processor machine (2x CPU E5-2650) running several = CPU-bound processes (ULE scheduler). >> 3 processes are 32-threaded, and 8 are single threaded. >>=20 >> I bind all 3 32-threaded processes to CPUs 0-24 (cpuset -C -l 0-24 -p = XXX). >>=20 >> I expect that the remaining 8 single-threaded processes will (mostly) = run on the remaining 25-31 CPU cores and use (almost) 100% cpu each. >>=20 >> But this is not the case (according to top(1)): they spend a lot of = time on 0-24 CPUs and CPU Idle time is about 10%. >>=20 >> These are all purely computational programs, in idle system = single-threaded programs steadily consume 100% of a core, and = 32-threaded programs consume all 32 cores and idle time is zero. >>=20 >> Is it an ULE scheduler feature or am I doing something wrong? >>=20 >> The goal is to give a single-threaded program a chance to run when = somebody started several 32-threaded processes. >=20 > You don't have 32 processor machine, you have only 16 processor > machine. > SMT/hyperthreading don't give real processor, SMT "CPU" have > unpredicable power and his load depend on load parent CPU. >=20 > For example, for my case I see such condition (simpliy) on CPU 0 and 1 > (SMT of one real core) with rise load: >=20 > load 0.1 0.1 > load 0.2 0.2 > load 0.3 0.3 > load 0.4 0.4 > load 0.45 0.45 > load 0.48 0.48 > load 1.00 1.00\ Yes I know about HT. But how does this explain why I have 10% of CPU = idle? If I explicitly bind my single-threaded processes to the remaining CPU = cores (25-32), they start to receive expected 100% of CPU and overall = Idle decreases. I just expect scheduler to do the same for me.
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