Re: [PATCH] sched/fair: don't NUMA balance for kthreads

From: Peter Zijlstra
Date: Tue May 26 2020 - 16:02:47 EST

On Tue, May 26, 2020 at 05:40:06PM +0100, Valentin Schneider wrote:

> > Change the task_tick_numa() check to exclude kernel threads in general,
> > as it doesn't make sense to attempt ot balance for kthreads anyway.
> >
> Does it? (this isn't a rethorical question)
> Suppose a given kthread ends up doing more accesses to some pages
> (via use_mm()) than the other threads that access them, wouldn't it make
> sense to take that into account when it comes to NUMA balancing?

Well, task_tick_numa() tries and farm off a bunch of actual work to
task_work_add(), and there's so very little userspace for a kernel
thread to return to... :-)