On 7/11/19 10:47 PM, Hillf Danton wrote:
>
> On Thu, 11 Jul 2019 02:42:56 +0800 Mike Kravetz wrote:
>>
>> It is quite easy to hit the condition where:
>> nr_reclaimed == 0 && nr_scanned == 0 is true, but we skip the previous test
>>
> Then skipping check of __GFP_RETRY_MAYFAIL makes no sense in your case.
> It is restored in respin below.
>
>> and the compaction check:
>> sc->nr_reclaimed < pages_for_compaction &&
>> inactive_lru_pages > pages_for_compaction
>> is true, so we return true before the below check of costly_fg_reclaim
>>
> This check is placed after COMPACT_SUCCESS; the latter is used to
> replace sc->nr_reclaimed < pages_for_compaction.
>
> And dryrun detection is added based on the result of last round of
> shrinking of inactive pages, particularly when their number is large
> enough.
>
Thanks Hillf.
This change does appear to eliminate the issue with stalls by
should_continue_reclaim returning true too often. I need to think
some more about exactly what is impacted with the change.
With this change, the problem moves to compaction with should_compact_retry
returning true too often. It is the same behavior seem when I simply removed
the __GFP_RETRY_MAYFAIL special casing in should_continue_reclaim.
At Mel's suggestion I removed the compaction_zonelist_suitable() call
from should_compact_retry. This eliminated the compaction stalls. Thanks
Mel.
With both changes, stalls appear to be eliminated. This is promising.
I'll try to refine these approaches and continue testing.
--
Mike Kravetz
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2571,18 +2571,6 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
> return false;
> }
>
> - /*
> - * If we have not reclaimed enough pages for compaction and the
> - * inactive lists are large enough, continue reclaiming
> - */
> - pages_for_compaction = compact_gap(sc->order);
> - inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
> - if (get_nr_swap_pages() > 0)
> - inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
> - if (sc->nr_reclaimed < pages_for_compaction &&
> - inactive_lru_pages > pages_for_compaction)
> - return true;
> -
> /* If compaction would go ahead or the allocation would succeed, stop */
> for (z = 0; z <= sc->reclaim_idx; z++) {
> struct zone *zone = &pgdat->node_zones[z];
> @@ -2598,7 +2586,21 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
> ;
> }
> }
> - return true;
> +
> + /*
> + * If we have not reclaimed enough pages for compaction and the
> + * inactive lists are large enough, continue reclaiming
> + */
> + pages_for_compaction = compact_gap(sc->order);
> + inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
> + if (get_nr_swap_pages() > 0)
> + inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
> +
> + return inactive_lru_pages > pages_for_compaction &&
> + /*
> + * avoid dryrun with plenty of inactive pages
> + */
> + nr_scanned && nr_reclaimed;
> }
>
> static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
> --
>
