Date: Sun, 13 Sep 2015 16:09:21 +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: <20150913130920.GR3158@zxy.spb.ru> In-Reply-To: <623FA99E-04E7-4D29-953A-61EE7B35CBF6@gmail.com> References: <623FA99E-04E7-4D29-953A-61EE7B35CBF6@gmail.com>
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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
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