Re: [PATCH 5/6] mm: kswapd: Treat zone->all_unreclaimable insleeping_prematurely similar to balance_pgdat()

[KAMEZAWA Hiroyuki]

On Fri, 10 Dec 2010 10:55:32 +0000
Mel Gorman <mel@xxxxxxxxx> wrote:

> On Fri, Dec 10, 2010 at 10:23:37AM +0900, KAMEZAWA Hiroyuki wrote:
> > On Thu,  9 Dec 2010 11:18:19 +0000
> > Mel Gorman <mel@xxxxxxxxx> wrote:
> > 
> > > After DEF_PRIORITY, balance_pgdat() considers all_unreclaimable zones to
> > > be balanced but sleeping_prematurely does not. This can force kswapd to
> > > stay awake longer than it should. This patch fixes it.
> > > 
> > > Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> > 
> > Hmm, maybe the logic works well but I don't like very much.
> > 
> > How about adding below instead of pgdat->node_present_pages ?
> > 
> > static unsigned long required_balanced_pages(pgdat, classzone_idx)
> > {
> > 	unsigned long present = 0;
> > 
> > 	for_each_zone_in_node(zone, pgdat) {
> > 		if (zone->all_unreclaimable) /* Ignore unreclaimable zone at checking balance */
> > 			continue;
> > 		if (zone_idx(zone) > classzone_idx)
> > 			continue;
> > 		present = zone->present_pages;
> > 	}
> > 	return present;
> > }
> > 
> 
> I'm afraid I do not really understand. After your earlier comments,
> pgdat_balanced() now looks like
> 
> static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
>                                                 int classzone_idx)
> {
>         unsigned long present_pages = 0;
>         int i;
> 
>         for (i = 0; i <= classzone_idx; i++)
>                 present_pages += pgdat->node_zones[i].present_pages;
> 
>         return balanced_pages > (present_pages >> 2);
> }
> 
> so the classzone is being taken into account. I'm not sure what you're
> asking for it to be changed to. Maybe it'll be clearer after V4 comes
> out rebased on top of mmotm.
> 

Ah, this seems okay to me.

Thank you.
-Kame



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