Messages in this thread | | | From | Joel Fernandes <> | Date | Wed, 4 Oct 2023 12:09:58 -0400 | Subject | Re: NOHZ interaction between IPI-less kick_ilb() and nohz_csd_func(). |
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+Frederic Weisbecker
On Wed, Sep 13, 2023 at 10:32 AM Suleiman Souhlal <suleiman@google.com> wrote: > > (I forgot to also add Vincent...) > > On Wed, Sep 13, 2023 at 9:49 PM Suleiman Souhlal <suleiman@google.com> wrote: > > > > Hello, > > > > I noticed that on x86 machines that have MWAIT, with NOHZ, when the > > kernel decides to kick the idle load balance on another CPU in > > kick_ilb(), there's an optimization that makes it avoid using an IPI > > and instead exploit the fact that the remote CPU is MWAITing on the > > thread_info flags, by just setting TIF_NEED_RESCHED, in > > call_function_single_prep_ipi(). > > However, on the remote CPU, in nohz_csd_func(), we end up not raising > > the sched softirq due to NEED_RESCHED being set, so the ILB doesn't > > end up getting done. > > > > Is this intended? > > > > Thanks, > > -- Suleiman
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