linux-kernel - Re: mm, vmscan: commit makes PAE kernel crash nightly (bisected)

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Date:   Tue, 17 Jan 2017 14:52:28 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Trevor Cordes <trevor@...nopolis.ca>, linux-kernel@...r.kernel.org,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: mm, vmscan: commit makes PAE kernel crash nightly (bisected)

On Mon 16-01-17 11:09:34, Mel Gorman wrote:
[...]
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 532a2a750952..46aac487b89a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2684,6 +2684,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
>  				continue;
>  
>  			if (sc->priority != DEF_PRIORITY &&
> +			    !buffer_heads_over_limit &&
>  			    !pgdat_reclaimable(zone->zone_pgdat))
>  				continue;	/* Let kswapd poll it */

I think we should rather remove pgdat_reclaimable here. This sounds like
a wrong layer to decide whether we want to reclaim and how much.

But even that won't help very much I am afraid. As I've noted in the
other response as long as we will scale the slab shrinking based on
nr_scanned we will have a problem with situations where slab outnumbers
lru lists too much. I do not have a good idea how to fix that though...

-- 
Michal Hocko
SUSE Labs