> On 13 сент. 2015 г., at 19:40, Slawa Olhovchenkov <s...@zxy.spb.ru> wrote: > > On Sun, Sep 13, 2015 at 04:44:40PM +0300, Dmitry Sivachenko wrote: > >> >>> On 13 сент. 2015 г., at 16:09, Slawa Olhovchenkov <s...@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.
Thanks for the explanation. In my example SMT pairs are numbered with sequential numbers, so 0+1 is one SMT group, 2+3 is second SMT group, and so on. So in 25-32 range there are several real CPU cores which remain idle while processes are fighting for overloaded 0-24. When I explicitly pin my single-threaded processes to 25-32 range, they start to receive 100% of CPU (and finish faster to be clear). _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
