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Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint

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On 01/04/2017 11:19 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> Our reclaim process has several tracepoints to tell us more about how
> things are progressing. We are, however, missing a tracepoint to track
> active list aging. Introduce mm_vmscan_lru_shrink_active which reports
> the number of
> 	- nr_scanned, nr_taken pages to tell us the LRU isolation
> 	  effectiveness.

Well, this point is no longer true, is it...

> 	- nr_referenced pages which tells us that we are hitting referenced
> 	  pages which are deactivated. If this is a large part of the
> 	  reported nr_deactivated pages then we might be hitting into
> 	  the active list too early because they might be still part of
> 	  the working set. This might help to debug performance issues.
> 	- nr_activated pages which tells us how many pages are kept on the

"nr_activated" is slightly misleading? They remain active, they are not
being activated (that's why the pgactivate vmstat is also not increased
on them, right?). I guess rename to "nr_active" ? Or something like
"nr_remain_active" although that's longer.

[...]

> @@ -1857,6 +1859,7 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
>  	unsigned long pgmoved = 0;
>  	struct page *page;
>  	int nr_pages;
> +	int nr_moved = 0;
>  
>  	while (!list_empty(list)) {
>  		page = lru_to_page(list);
> @@ -1882,11 +1885,15 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
>  				spin_lock_irq(&pgdat->lru_lock);
>  			} else
>  				list_add(&page->lru, pages_to_free);
> +		} else {
> +			nr_moved += nr_pages;
>  		}
>  	}
>  
>  	if (!is_active_lru(lru))
>  		__count_vm_events(PGDEACTIVATE, pgmoved);

So we now have pgmoved and nr_moved. One is used for vmstat, other for
tracepoint, and the only difference is that vmstat includes pages where
we raced with page being unmapped from all pte's (IIUC?) and thus
removed from lru, which should be rather rare? I guess those are being
counted into vmstat only due to how the code evolved from using pagevec.
If we don't consider them in the tracepoint, then I'd suggest we don't
count them into vmstat either, and simplify this.

> +
> +	return nr_moved;
>  }
>  
>  static void shrink_active_list(unsigned long nr_to_scan,
> @@ -1902,7 +1909,8 @@ static void shrink_active_list(unsigned long nr_to_scan,
>  	LIST_HEAD(l_inactive);
>  	struct page *page;
>  	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
> -	unsigned long nr_rotated = 0;
> +	unsigned nr_deactivate, nr_activate;
> +	unsigned nr_rotated = 0;
>  	isolate_mode_t isolate_mode = 0;
>  	int file = is_file_lru(lru);
>  	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> @@ -1980,13 +1988,15 @@ static void shrink_active_list(unsigned long nr_to_scan,
>  	 */
>  	reclaim_stat->recent_rotated[file] += nr_rotated;
>  
> -	move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
> -	move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
> +	nr_activate = move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
> +	nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
>  	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
>  	spin_unlock_irq(&pgdat->lru_lock);
>  
>  	mem_cgroup_uncharge_list(&l_hold);
>  	free_hot_cold_page_list(&l_hold, true);
> +	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
> +			nr_deactivate, nr_rotated, sc->priority, file);
>  }
>  
>  /*
> 

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[PATCH 0/7 v2] vm, vmscan: enahance vmscan tracepoints Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
  [PATCH 2/7] mm, vmscan: add active list aging tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
    Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Vlastimil Babka <vbabka@suse.cz> - 2017-01-04 14:10 +0100
      Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 14:20 +0100
        Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Vlastimil Babka <vbabka@suse.cz> - 2017-01-04 14:50 +0100
    Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 15:00 +0100
      Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint Minchan Kim <minchan@kernel.org> - 2017-01-05 06:50 +0100
  [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
    Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate  tracepoint Minchan Kim <minchan@kernel.org> - 2017-01-05 07:10 +0100
      Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate  tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-05 11:20 +0100
        Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate  tracepoint Mel Gorman <mgorman@suse.de> - 2017-01-05 16:00 +0100
          Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate  tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-05 16:20 +0100
  [PATCH 3/7] mm, vmscan: show the number of skipped pages in mm_vmscan_lru_isolate Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
  [PATCH 6/7] mm, vmscan: enhance mm_vmscan_lru_shrink_inactive tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
  [PATCH 5/7] mm, vmscan: extract shrink_page_list reclaim counters into a struct Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
    Re: [PATCH 5/7] mm, vmscan: extract shrink_page_list reclaim counters  into a struct Vlastimil Babka <vbabka@suse.cz> - 2017-01-04 16:00 +0100
      Re: [PATCH 5/7] mm, vmscan: extract shrink_page_list reclaim  counters into a struct Michal Hocko <mhocko@kernel.org> - 2017-01-04 16:20 +0100
  [PATCH 7/7] mm, vmscan: add mm_vmscan_inactive_list_is_low tracepoint Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:30 +0100
  Re: [PATCH 0/7 v2] vm, vmscan: enahance vmscan tracepoints Michal Hocko <mhocko@kernel.org> - 2017-01-04 11:40 +0100
  Re: [PATCH 0/7 v2] vm, vmscan: enahance vmscan tracepoints Vlastimil Babka <vbabka@suse.cz> - 2017-01-05 09:30 +0100
  Re: [PATCH 0/7 v2] vm, vmscan: enahance vmscan tracepoints Michal Hocko <mhocko@kernel.org> - 2017-01-05 11:50 +0100

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