Re: [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone

[Mel Gorman]

On Fri, Jun 17, 2016 at 12:46:05PM +0200, Vlastimil Babka wrote:
> On 06/09/2016 08:04 PM, Mel Gorman wrote:
> >kswapd is woken when zones are below the low watermark but the wakeup
> >decision is not taking the classzone into account.  Now that reclaim is
> >node-based, it is only required to wake kswapd once per node and only if
> >all zones are unbalanced for the requested classzone.
> >
> >Note that one node might be checked multiple times but there is no cheap
> >way of tracking what nodes have already been visited for zoneslists that
> >be ordered by either zone or node.
> 
> Wouldn't it be possible to optimize for node order as you did in direct
> reclaim? Do the zone_balanced checks when going through zonelist, and once
> node changes in iteration, wake up if no eligible zones visited so far were
> balanced.
> 

Yeah, it is. I'll chuck it in.

-- 
Mel Gorman
SUSE Labs