On Fri, May 31, 2019 at 3:45 PM Aaron Lu <aaron...@linux.alibaba.com> wrote: > > On Fri, May 31, 2019 at 02:53:21PM +0800, Aubrey Li wrote: > > On Fri, May 31, 2019 at 2:09 PM Aaron Lu <aaron...@linux.alibaba.com> wrote: > > > > > > On 2019/5/31 13:12, Aubrey Li wrote: > > > > On Fri, May 31, 2019 at 11:01 AM Aaron Lu <aaron...@linux.alibaba.com> > > > > wrote: > > > >> > > > >> This feels like "date" failed to schedule on some CPU > > > >> on time. > > > >> > > > >> My first reaction is: when shell wakes up from sleep, it will > > > >> fork date. If the script is untagged and those workloads are > > > >> tagged and all available cores are already running workload > > > >> threads, the forked date can lose to the running workload > > > >> threads due to __prio_less() can't properly do vruntime comparison > > > >> for tasks on different CPUs. So those idle siblings can't run > > > >> date and are idled instead. See my previous post on this: > > > >> https://lore.kernel.org/lkml/20190429033620.GA128241@aaronlu/ > > > >> (Now that I re-read my post, I see that I didn't make it clear > > > >> that se_bash and se_hog are assigned different tags(e.g. hog is > > > >> tagged and bash is untagged). > > > > > > > > Yes, script is untagged. This looks like exactly the problem in you > > > > previous post. I didn't follow that, does that discussion lead to a > > > > solution? > > > > > > No immediate solution yet. > > > > > > >> > > > >> Siblings being forced idle is expected due to the nature of core > > > >> scheduling, but when two tasks belonging to two siblings are > > > >> fighting for schedule, we should let the higher priority one win. > > > >> > > > >> It used to work on v2 is probably due to we mistakenly > > > >> allow different tagged tasks to schedule on the same core at > > > >> the same time, but that is fixed in v3. > > > > > > > > I have 64 threads running on a 104-CPU server, that is, when the > > > > > > 104-CPU means 52 cores I guess. > > > 64 threads may(should?) spread on all the 52 cores and that is enough > > > to make 'date' suffer. > > > > 64 threads should spread onto all the 52 cores, but why they can get > > scheduled while untagged "date" can not? Is it because in the current > > If 'date' didn't get scheduled, there will be no output at all unless > all those workload threads finished :-)
Certainly I meant untagged "date" can not be scheduled on time, :) > > I guess the workload you used is not entirely CPU intensive, or 'date' > can be totally blocked due to START_DEBIT. But note that START_DEBIT > isn't the problem here, cross CPU vruntime comparison is. > > > implementation the task with cookie always has higher priority than the > > task without a cookie? > > No. I checked the benchmark log manually, it looks like the data of two benchmarks with cookies are acceptable, but ones without cookies are really bad.