Messages in this thread | | | Date | Wed, 4 Jan 2017 14:16:55 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint |
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On Wed 04-01-17 13:52:24, Vlastimil Babka wrote: > 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...
ups, leftover - nr_take - the number of isolated pages
> > - 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.
will go with nr_active
> > [...] > > > @@ -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.
OK, but I would prefer to have this in a separate patch, OK? -- Michal Hocko SUSE Labs
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