Re: [Xen-devel] [PATCH 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently

[Nadav Amit <namit@xxxxxxxxxx>]

> On Jun 25, 2019, at 8:00 PM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> 
> On 6/25/19 7:35 PM, Nadav Amit wrote:
>>>> const struct flush_tlb_info *f = info;
>>>> +  enum tlb_flush_reason reason;
>>>> +
>>>> +  reason = (f->mm == NULL) ? TLB_LOCAL_SHOOTDOWN : TLB_LOCAL_MM_SHOOTDOWN;
>>> 
>>> Should we just add the "reason" to flush_tlb_info?  It's OK-ish to imply
>>> it like this, but seems like it would be nicer and easier to track down
>>> the origins of these things if we did this at the caller.
>> 
>> I prefer not to. I want later to inline flush_tlb_info into the same
>> cacheline that holds call_function_data. Increasing the size of
>> flush_tlb_info for no good reason will not help…
> 
> Well, flush_tlb_info is at 6/8ths of a cacheline at the moment.
> call_function_data is 3/8ths.  To me, that means we have some slack in
> the size.

I do not understand your math.. :(

6 + 3 > 8 so putting both flush_tlb_info and call_function_data does not
leave us any slack (we can save one qword, so we can actually put them
at the same cacheline).

You can see my current implementation here:

https://lore.kernel.org/lkml/20190531063645.4697-4-namit@xxxxxxxxxx/T/#m0ab5fe0799ba9ff0d41197f1095679fe26aebd57
https://lore.kernel.org/lkml/20190531063645.4697-4-namit@xxxxxxxxxx/T/#m7b35a93dffd23fbb7ca813c795a0777d4cdcb51b

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