Re: needed lru_add_drain_all() change

(2012/06/28 15:23), KOSAKI Motohiro wrote:

On Tue, Jun 26, 2012 at 5:37 PM, Andrew Morton
[off-list ref] wrote:

quoted

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








--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>