process scheduling and cpuset

[Dmitry Sivachenko]

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.

Thanks!