Messages in this thread | | | From | Lai Jiangshan <> | Date | Wed, 23 Dec 2020 23:01:53 +0800 | Subject | Re: [PATCH -tip V2 00/10] workqueue: break affinity initiatively |
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On Wed, Dec 23, 2020 at 5:39 AM Dexuan-Linux Cui <dexuan.linux@gmail.com> wrote: > > On Fri, Dec 18, 2020 at 8:11 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote: > > > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > > > 06249738a41a ("workqueue: Manually break affinity on hotplug") > > said that scheduler will not force break affinity for us. > > > > But workqueue highly depends on the old behavior. Many parts of the codes > > relies on it, 06249738a41a ("workqueue: Manually break affinity on hotplug") > > is not enough to change it, and the commit has flaws in itself too. > > > > It doesn't handle for worker detachment. > > It doesn't handle for worker attachement, mainly worker creation > > which is handled by Valentin Schneider's patch [1]. > > It doesn't handle for unbound workers which might be possible > > per-cpu-kthread. > > > > We need to thoroughly update the way workqueue handles affinity > > in cpu hot[un]plug, what is this patchset intends to do and > > replace the Valentin Schneider's patch [1]. The equivalent patch > > is patch 10. > > > > Patch 1 fixes a flaw reported by Hillf Danton <hdanton@sina.com>. > > I have to include this fix because later patches depends on it. > > > > The patchset is based on tip/master rather than workqueue tree, > > because the patchset is a complement for 06249738a41a ("workqueue: > > Manually break affinity on hotplug") which is only in tip/master by now. > > > > And TJ acked to route the series through tip. > > > > Changed from V1: > > Add TJ's acked-by for the whole patchset > > > > Add more words to the comments and the changelog, mainly derived > > from discussion with Peter. > > > > Update the comments as TJ suggested. > > > > Update a line of code as Valentin suggested. > > > > Add Valentin's ack for patch 10 because "Seems alright to me." and > > add Valentin's comments to the changelog which is integral. > > > > [1]: https://lore.kernel.org/r/ff62e3ee994efb3620177bf7b19fab16f4866845.camel@redhat.com > > [V1 patcheset]: https://lore.kernel.org/lkml/20201214155457.3430-1-jiangshanlai@gmail.com/ > > > > Cc: Hillf Danton <hdanton@sina.com> > > Cc: Valentin Schneider <valentin.schneider@arm.com> > > Cc: Qian Cai <cai@redhat.com> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Vincent Donnefort <vincent.donnefort@arm.com> > > Cc: Tejun Heo <tj@kernel.org> > > > > Lai Jiangshan (10): > > workqueue: restore unbound_workers' cpumask correctly > > workqueue: use cpu_possible_mask instead of cpu_active_mask to break > > affinity > > workqueue: Manually break affinity on pool detachment > > workqueue: don't set the worker's cpumask when kthread_bind_mask() > > workqueue: introduce wq_online_cpumask > > workqueue: use wq_online_cpumask in restore_unbound_workers_cpumask() > > workqueue: Manually break affinity on hotplug for unbound pool > > workqueue: reorganize workqueue_online_cpu() > > workqueue: reorganize workqueue_offline_cpu() unbind_workers() > > workqueue: Fix affinity of kworkers when attaching into pool > > > > kernel/workqueue.c | 214 ++++++++++++++++++++++++++++----------------- > > 1 file changed, 132 insertions(+), 82 deletions(-) > > > > -- > > 2.19.1.6.gb485710b > > Hi, > I tested this patchset on today's tip.git's master branch > (981316394e35 ("Merge branch 'locking/urgent'")). > > Every time the kernel boots with 32 CPUs (I'm running the Linux VM on > Hyper-V), I get the below warning. > (BTW, with 8 or 16 CPUs, I don't see the warning). > By printing the cpumasks with "%*pbl", I know the warning happens because: > new_mask = 16-31 > cpu_online_mask= 0-16 > cpu_active_mask= 0-15 > p->nr_cpus_allowed=16 > > 2374 if (p->flags & PF_KTHREAD) { > 2375 /* > 2376 * For kernel threads that do indeed end up on online && > 2377 * !active we want to ensure they are strict > per-CPU threads. > 2378 */ > 2379 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) && > 2380 !cpumask_intersects(new_mask, cpu_active_mask) && > 2381 p->nr_cpus_allowed != 1); > 2382 } > 2383 >
Hello, Dexuan
Could you omit patch4 of the patchset and test it again, please? ("workqueue: don't set the worker's cpumask when kthread_bind_mask()")
kthread_bind_mask() set the worker task to the pool's cpumask without any check. And set_cpus_allowed_ptr() finds that the task's cpumask is unchanged (already set by kthread_bind_mask()) and skips all the checks.
And I found that numa=fake=2U seems broken on cpumask_of_node() in my box.
Thanks, Lai
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