linux-kernel - Re: [PATCH] mm: memcontrol: add file_thp, shmem

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Date:   Thu, 22 Oct 2020 14:29:34 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Rik van Riel <riel@...riel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH] mm: memcontrol: add file_thp, shmem_thp to memory.stat

On Thu, Oct 22, 2020 at 12:57:55PM -0400, Rik van Riel wrote:
> On Thu, 2020-10-22 at 12:49 -0400, Rik van Riel wrote:
> > On Thu, 2020-10-22 at 11:18 -0400, Johannes Weiner wrote:
> > 
> > > index e80aa9d2db68..334ce608735c 100644
> > > --- a/mm/filemap.c
> > > +++ b/mm/filemap.c
> > > @@ -204,9 +204,9 @@ static void unaccount_page_cache_page(struct
> > > address_space *mapping,
> > >  	if (PageSwapBacked(page)) {
> > >  		__mod_lruvec_page_state(page, NR_SHMEM, -nr);
> > >  		if (PageTransHuge(page))
> > > -			__dec_node_page_state(page, NR_SHMEM_THPS);
> > > +			__dec_lruvec_page_state(page, NR_SHMEM_THPS);
> > >  	} else if (PageTransHuge(page)) {
> > > -		__dec_node_page_state(page, NR_FILE_THPS);
> > > +		__dec_lruvec_page_state(page, NR_FILE_THPS);
> > >  		filemap_nr_thps_dec(mapping);
> > >  	}
> > 
> > This may be a dumb question, but does that mean the
> > NR_FILE_THPS number will no longer be visible in
> > /proc/vmstat or is there some magic I overlooked in
> > a cursory look of the code?
> 
> Never mind, I found it a few levels deep in
> __dec_lruvec_page_state.

No worries, it's a legit question.

lruvec is at the intersection of node and memcg, so I'm just moving
the accounting to a higher-granularity function that updates all
layers, including the node.

> Reviewed-by: Rik van Riel <riel@...riel.com>

Thanks!