Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabledwhile isolating pages for migration

From: KAMEZAWA Hiroyuki
Date: Mon Feb 28 2011 - 01:00:53 EST

On Mon, 28 Feb 2011 06:48:18 +0100
Andrea Arcangeli <aarcange@xxxxxxxxxx> 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).


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