Re: [PATCH v3 4/4] arm64: support batched/deferred tlb shootdown during page reclamation

On Tue, Sep 20, 2022 at 3:00 PM Anshuman Khandual
[off-list ref] wrote:

On 8/22/22 13:51, Yicong Yang wrote:

quoted

+static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
+{
+     return true;
+}

This needs to be conditional on systems, where there will be performance
improvements, and should not just be enabled all the time on all systems.
num_online_cpus() > X, which does not hold any cpu hotplug lock would be
a good metric ?

for a small system, i don't see how this patch will help, e.g. cpus <= 4;
so we can actually disable tlb-batch on small systems.
just need to check if we will have any race condition since hotplug will
make the condition true and false dynamically.

Thanks
Barry