> On 13 ????. 2015 ?., at 16:09, Slawa Olhovchenkov <slw at 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.