Messages in this thread | | | Date | Thu, 20 Oct 2022 19:08:13 +0200 | From | Peter Zijlstra <> | Subject | Re: [RESEND] sched/fair: Add min_ratio for cfs bandwidth_control |
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On Wed, Oct 19, 2022 at 11:21:19AM -1000, Tejun Heo wrote: > Hello, > > On Wed, Oct 19, 2022 at 11:15:51AM +0800, Chuyi Zhou wrote: > > Tasks may be throttled when holding locks for a long time by current > > cfs bandwidth control mechanism once users set a too small quota/period > > ratio, which can result whole system get stuck[1]. > > > > In order to prevent the above situation from happening, this patch adds > > sysctl_sched_cfs_bandwidth_min_ratio in /proc/sys/kernel, which indicates > > the minimum percentage of quota/period users can set. The default value is > > zero and users can set quota and period without triggering this constraint. > > > > Link[1]:https://lore.kernel.org/lkml/5987be34-b527-4ff5-a17d-5f6f0dc94d6d@huawei.com/T/ > > Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> > > Suggested-by: Abel Wu <wuyun.abel@bytedance.com> > > This is a bit of a bandaid. I think what we really need to do is only > throttling when running in userspace. In kernel space, it should just keep > accumulating used cycles as debt which should be paid back before userspace > code can run again so that we don't throttle at random places in the kernel.
That's just moving the problem. But yeah; perhaps. Starving random userspace is less of a problem I suppose.
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