linux-kernel - Re: [PATCH 3/6] mm/page_alloc: Split out buddy removal code from rmqueue into separate helper

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Date:   Wed, 25 May 2022 12:23:34 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 3/6] mm/page_alloc: Split out buddy removal code from
 rmqueue into separate helper

On 05/24/22 12:55, Mel Gorman wrote:
> On Mon, May 23, 2022 at 05:09:21PM +0100, Qais Yousef wrote:
> > On 05/12/22 09:50, Mel Gorman wrote:
> > > This is a preparation page to allow the buddy removal code to be reused
> > > in a later patch.
> > > 
> > > No functional change.
> > > 
> > > Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> > > Tested-by: Minchan Kim <minchan@...nel.org>
> > > Acked-by: Minchan Kim <minchan@...nel.org>
> > > ---
> > 
> > I see this splat when this patch is applied on 5.10.107 kernel:
> > 
> 
> <SNIP>
> 
> > I could resolve it by applying this patch:
> > 
> > 	diff --git a/mm/vmstat.c b/mm/vmstat.c
> > 	index 80c1e0a0f094e..92fb0c08296ef 100644
> > 	--- a/mm/vmstat.c
> > 	+++ b/mm/vmstat.c
> > 	@@ -957,11 +957,11 @@ void __inc_numa_state(struct zone *zone,
> > 		u16 __percpu *p = pcp->vm_numa_stat_diff + item;
> > 		u16 v;
> > 
> > 	-       v = __this_cpu_inc_return(*p);
> > 	+       v = this_cpu_inc_return(*p);
> > 
> > 		if (unlikely(v > NUMA_STATS_THRESHOLD)) {
> > 			zone_numa_state_add(v, zone, item);
> > 	-               __this_cpu_write(*p, 0);
> > 	+               this_cpu_write(*p, 0);
> > 		}
> > 	 }
> > 
> 
> 5.18 does not have __inc_numa_state() so it's likely you are missing
> backports, probably f19298b9516c1a031b34b4147773457e3efe743b at minimum.

Thanks Mel. Sorry it seems I stopped my analysis tad too soon. It seems the
dependency chain is more than that commit. I couldn't backport it on its own.

I just happened to be an accidental user of that kernel (it's an Android 5.10
tree). I did report it there too, but I thought (wrongly) this could benefit
this upstream discussion.

I'll take it there.

Thanks!

--
Qais Yousef