Re: [PATCH 3/3] mm: page allocator: Reconsider zones for allocationafter direct reclaim
From: KOSAKI Motohiro
Date: Thu Jul 21 2011 - 05:35:55 EST
>> So, I think we don't need to care zonelist, just kswapd turn off
>> their own node.
> I don't understand what you mean by this.
This was the answer of following your comments.
> Instead, couldn't we turn zlc->fullzones off from kswapd?
> > Which zonelist should it clear (there are two)
I mean, buddy list is belong to zone, not zonelist. therefore, kswapd
don't need to look up zonelist.
So, I'd suggest either following way,
- use direct reclaim path, but only clear a zlc bit of zones in reclaimed zonelist, not all. or
- use kswapd and only clear a zlc bit at kswap exiting balance_pgdat
I'm prefer to add a branch to slowpath (ie reclaim path) rather than fast path.
>> And, just curious, If we will have a proper zlc clear point, why
>> do we need to keep HZ timeout?
> Yes because we are not guaranteed to call direct reclaim either. Memory
> could be freed by a process exiting and I'd rather not add cost to
> the free path to find and clear all zonelists referencing the zone the
> page being freed belongs to.
Ok, it's good trade-off. I agree we need to keep HZ timeout.
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