> On Oct 30, 2023, at 7:55 PM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > !! External Email > > On 10/30/23 00:25, Byungchul Park wrote: >> I'm suggesting a mechanism to reduce TLB flushes by keeping source and >> destination of folios participated in the migrations until all TLB >> flushes required are done, only if those folios are not mapped with >> write permission PTE entries at all. I worked Based on v6.6-rc5. > > There's a lot of common overhead here, on top of the complexity in general: > > * A new page flag > * A new cpumask_t in task_struct > * A new zone list > * Extra (temporary) memory consumption > > and the benefits are ... "performance improved a little bit" on one > workload. That doesn't seem like a good overall tradeoff to me. I almost forgot that I did (and embarrassingly did not follow) a TLB flush deferring mechanism mechanism before [*], which was relatively generic. I did not look at the migration case, but it could have been relatively easily added - I think. Feel free to plagiarize if you find it suitable. Note that some of the patch-set is not relevant (e.g., 20/20 has already been fixed, 3/20 was merged.) [*] https://lore.kernel.org/linux-mm/20210131001132.3368247-1-namit@xxxxxxxxxx/
