Messages in this thread | | | Date | Fri, 24 Mar 2023 15:13:00 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs |
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On Wed, Mar 22, 2023 at 04:11:44PM +0200, ypodemsk@redhat.com wrote: > On Mon, 2023-03-20 at 09:49 +0100, Peter Zijlstra wrote: > > On Sun, Mar 12, 2023 at 10:09:45AM +0200, Yair Podemsky wrote: > > > Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs > > > indiscriminately, this causes unnecessary work and delays notable > > > in > > > real-time use-cases and isolated cpus, this patch will limit this > > > IPI to > > > only be sent to cpus referencing the effected mm and are currently > > > in > > > kernel space. > > > > Did you validate that all architectures for which this is relevant > > actually set bits in mm_cpumask() ? > > > Hi Peter, > Thank you for bringing this to my attention. > I reviewed the architectures using the MMU_GATHER_RCU_TABLE_FREE: > arm, powerpc, s390, sparc and x86 set the bit when switching process > in. > for arm64 removed set/clear bit in 38d96287504a ("arm64: mm: kill > mm_cpumask usage") > The reason given was that mm_cpumask was not used. > Given that we now have a use for it, I will add a patch to revert.
Maintaining the mask is also not free, so I'm not keen on adding it back unless there's a net win.
Will
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