Re: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of siblingsof SMT

[Alex Shi]

>>
>> I just measured the cost of this function on my Romely EP(32 LCPUs) with
>> cpumask_t and NR_CPUS = 32/256/512/4096, the cost are similar with
>> 256/512/4096 and that increased about 20% time cost from 32.
>>
>> I also tried to use cpumask_var_t and alloc it in heap(use
>> CPUMASK_OFFSTACK), actually, it cost same time with cpumask_t in stack.
>> But, the allocation bring another big cost. So, I use cpumask_t in stack.
>> The performance gain data in commit log is getting with NR_CPUS = 256.
> 
> Perhaps using a per-CPU cpumask would be the better choice here


See.

> (I can't see how preemption could validly be enabled when this
> code is utilized).


Sorry, What's your meaning here?, the function is always in pre-empt
safe mode.

> 
> Jan
> 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/