Re: needed lru_add_drain_all() change

[Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

(2012/06/28 15:23), KOSAKI Motohiro wrote:
> On Tue, Jun 26, 2012 at 5:37 PM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
>> https://bugzilla.kernel.org/show_bug.cgi?id=43811
>>
>> lru_add_drain_all() uses schedule_on_each_cpu().  But
>> schedule_on_each_cpu() hangs if a realtime thread is spinning, pinned
>> to a CPU.  There's no intention to change the scheduler behaviour, so I
>> think we should remove schedule_on_each_cpu() from the kernel.
>>
>> The biggest user of schedule_on_each_cpu() is lru_add_drain_all().
>>
>> Does anyone have any thoughts on how we can do this?  The obvious
>> approach is to declare these:
>>
>> static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
>> static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
>> static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
>>
>> to be irq-safe and use on_each_cpu().  lru_rotate_pvecs is already
>> irq-safe and converting lru_add_pvecs and lru_deactivate_pvecs looks
>> pretty simple.
>>
>> Thoughts?
>
> I agree.
>
> But i hope more. In these days, we have plenty lru_add_drain_all()
> callsite. So,
> i think we should remove struct pagevec and should aim migration aware new
> batch mechanism. maybe. This also improve compaction success rate.
>

migration-aware means an framework which isolate_xxxx_page() can work with ?
To do that, we need to know which object points to the page. Hmm. Do you have
anyidea ?

-Kame








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