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

[Anshuman Khandual]

On 9/15/22 20:01, Nadav Amit wrote:
> 
> 
>> On Sep 14, 2022, at 11:42 PM, Barry Song <21cnbao at gmail.com> wrote:
>>
>>>
>>> The very idea behind TLB deferral is the opportunity it (might) provide
>>> to accumulate address ranges and cpu masks so that individual TLB flush
>>> can be replaced with a more cost effective range based TLB flush. Hence
>>> I guess unless address range or cpumask based cost effective TLB flush
>>> is available, deferral does not improve the unmap performance as much.
>>
>>
>> After sending tlbi, if we wait for the completion of tlbi, we have to get Ack
>> from all cpus in the system, tlbi is not scalable. The point here is that we
>> avoid waiting for each individual TLBi. Alternatively, they are batched. If
>> you read the benchmark in the commit log, you can find the great decline
>> in the cost to swap out a page.
> 
> Just a minor correction: arch_tlbbatch_flush() does not collect ranges.
> On x86 it only accumulate CPU mask.

Thanks Nadav for the clarification.