linux-kernel - Re: [RFC][PATCH 6/9] mm/vmscan: add page demotion counter

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Date:   Mon, 19 Oct 2020 15:37:55 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <yang.shi@...ux.alibaba.com>, <rientjes@...gle.com>,
        <dan.j.williams@...el.com>, <david@...hat.com>
Subject: Re: [RFC][PATCH 6/9] mm/vmscan: add page demotion counter

Dave Hansen <dave.hansen@...ux.intel.com> writes:

> From: Yang Shi <yang.shi@...ux.alibaba.com>
>
> Account the number of demoted pages into reclaim_state->nr_demoted.

It appears that you don't add "nr_demoted" into struct reclaim_state.

> Add pgdemote_kswapd and pgdemote_direct VM counters showed in
> /proc/vmstat.
>
> [ daveh:
>    - __count_vm_events() a bit, and made them look at the THP
>      size directly rather than getting data from migrate_pages()

It appears that we get the data from migrate_pages() now.

> ]
>
> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: David Hildenbrand <david@...hat.com>
> ---
>
>  b/include/linux/vm_event_item.h |    2 ++
>  b/mm/vmscan.c                   |    6 ++++++
>  b/mm/vmstat.c                   |    2 ++
>  3 files changed, 10 insertions(+)
>
> diff -puN include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter include/linux/vm_event_item.h
> --- a/include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.171642439 -0700
> +++ b/include/linux/vm_event_item.h	2020-10-07 09:15:32.179642439 -0700
> @@ -33,6 +33,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
>  		PGREUSE,
>  		PGSTEAL_KSWAPD,
>  		PGSTEAL_DIRECT,
> +		PGDEMOTE_KSWAPD,
> +		PGDEMOTE_DIRECT,
>  		PGSCAN_KSWAPD,
>  		PGSCAN_DIRECT,
>  		PGSCAN_DIRECT_THROTTLE,
> diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
> --- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.173642439 -0700
> +++ b/mm/vmscan.c	2020-10-07 09:15:32.180642439 -0700
> @@ -147,6 +147,7 @@ struct scan_control {
>  		unsigned int immediate;
>  		unsigned int file_taken;
>  		unsigned int taken;
> +		unsigned int demoted;

It appears that this newly added field isn't used in the patch.

>  	} nr;
>  
>  	/* for recording the reclaimed slab by now */
> @@ -1134,6 +1135,11 @@ static unsigned int demote_page_list(str
>  			    target_nid, MIGRATE_ASYNC, MR_DEMOTION,
>  			    &nr_succeeded);
>  
> +	if (current_is_kswapd())
> +		__count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
> +	else
> +		__count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
> +
>  	return nr_succeeded;
>  }
>  
> diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
> --- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter	2020-10-07 09:15:32.175642439 -0700
> +++ b/mm/vmstat.c	2020-10-07 09:15:32.181642439 -0700
> @@ -1244,6 +1244,8 @@ const char * const vmstat_text[] = {
>  	"pgreuse",
>  	"pgsteal_kswapd",
>  	"pgsteal_direct",
> +	"pgdemote_kswapd",
> +	"pgdemote_direct",
>  	"pgscan_kswapd",
>  	"pgscan_direct",
>  	"pgscan_direct_throttle",
> _

Best Regards,
Huang, Ying