On 24.06.2019 15:30, Yafang Shao wrote: > On Mon, Jun 24, 2019 at 4:53 PM Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote: >> >> On 21.06.2019 13:14, Yafang Shao wrote: >>> There're six different reclaim paths by now, >>> - kswapd reclaim path >>> - node reclaim path >>> - hibernate preallocate memory reclaim path >>> - direct reclaim path >>> - memcg reclaim path >>> - memcg softlimit reclaim path >>> >>> The slab caches reclaimed in these paths are only calculated in the above >>> three paths. >>> >>> There're some drawbacks if we don't calculate the reclaimed slab caches. >>> - The sc->nr_reclaimed isn't correct if there're some slab caches >>> relcaimed in this path. >>> - The slab caches may be reclaimed thoroughly if there're lots of >>> reclaimable slab caches and few page caches. >>> Let's take an easy example for this case. >>> If one memcg is full of slab caches and the limit of it is 512M, in >>> other words there're approximately 512M slab caches in this memcg. >>> Then the limit of the memcg is reached and the memcg reclaim begins, >>> and then in this memcg reclaim path it will continuesly reclaim the >>> slab caches until the sc->priority drops to 0. >>> After this reclaim stops, you will find there're few slab caches left, >>> which is less than 20M in my test case. >>> While after this patch applied the number is greater than 300M and >>> the sc->priority only drops to 3. >>> >>> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> >>> --- >>> mm/vmscan.c | 7 +++++++ >>> 1 file changed, 7 insertions(+) >>> >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 18a66e5..d6c3fc8 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -3164,11 +3164,13 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, >>> if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask)) >>> return 1; >>> >>> + current->reclaim_state = &sc.reclaim_state; >>> trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask); >>> >>> nr_reclaimed = do_try_to_free_pages(zonelist, &sc); >>> >>> trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); >>> + current->reclaim_state = NULL; >> >> Shouldn't we remove reclaim_state assignment from __perform_reclaim() after this? >> > > Oh yes. We should remove it. Thanks for pointing out. > I will post a fix soon. With the change above, feel free to add my Reviewed-by: to all of the series. Kirill
