Date: Sun, 13 Sep 2015 19:40:57 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Dmitry Sivachenko <trtrmitya@gmail.com> Cc: FreeBSD Stable ML <stable@freebsd.org> Subject: Re: process scheduling and cpuset Message-ID: <20150913164057.GT21849@zxy.spb.ru> In-Reply-To: <C6ADA4B7-1126-44A5-94B3-97FA79C8582A@gmail.com> References: <623FA99E-04E7-4D29-953A-61EE7B35CBF6@gmail.com> <20150913130920.GR3158@zxy.spb.ru> <C6ADA4B7-1126-44A5-94B3-97FA79C8582A@gmail.com>
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On Sun, Sep 13, 2015 at 04:44:40PM +0300, Dmitry Sivachenko wrote: > > > On 13 сент. 2015 г., at 16:09, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote: > > > > On Sun, Sep 13, 2015 at 02:52:08PM +0300, Dmitry Sivachenko wrote: > > > >> Hello, > >> > >> 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. > >> > >> I bind all 3 32-threaded processes to CPUs 0-24 (cpuset -C -l 0-24 -p XXX). > >> > >> 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. > >> > >> 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%. > >> > >> 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. > >> > >> Is it an ULE scheduler feature or am I doing something wrong? > >> > >> The goal is to give a single-threaded program a chance to run when somebody started several 32-threaded processes. > > > > 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. > > > > For example, for my case I see such condition (simpliy) on CPU 0 and 1 > > (SMT of one real core) with rise load: > > > > 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. > Idle is not goal, goal is lessing task executing time.
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