process scheduling and cpuset
trtrmitya at gmail.com
Sun Sep 13 13:44:46 UTC 2015
> On 13 сент. 2015 г., at 16:09, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:
> On Sun, Sep 13, 2015 at 02:52:08PM +0300, Dmitry Sivachenko wrote:
>> 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
> 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.
More information about the freebsd-stable