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SubjectRe: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration
On Mon, 28 Feb 2011 06:48:18 +0100
Andrea Arcangeli <aarcange@redhat.com> wrote:

> On Mon, Feb 28, 2011 at 11:17:46AM +0900, KAMEZAWA Hiroyuki wrote:
> > BTW, I forget why we always take zone->lru_lock with IRQ disabled....
>
> To decrease lock contention in SMP to deliver overall better
> performance (not sure how much it helps though). It was supposed to be
> hold for a very short time (PAGEVEC_SIZE) to avoid giving irq latency
> problems.
>

memory hotplug uses MIGRATE_ISOLATED migrate types for scanning pfn range
without lru_lock. I wonder whether we can make use of it (the function
which memory hotplug may need rework for the compaction but migrate_type can
be used, I think).

Hmm.
-Kame



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