From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: mm: remove unnecessary back-off function when retrying page reclaim The backoff mechanism is not needed. If we have MAX_RECLAIM_RETRIES loops without progress, we'll OOM anyway; backing off might cut one or two iterations off that in the rare OOM case. If we have intermittent success reclaiming a few pages, the backoff function gets reset also, and so is of little help in these scenarios. We might want a backoff function for when there IS progress, but not enough to be satisfactory. But this isn't that. Remove it. Link: http://lkml.kernel.org/r/20170228214007.5621-10-hannes@xxxxxxxxxxx Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Jia He <hejianet@xxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff -puN mm/page_alloc.c~mm-remove-unnecessary-back-off-function-when-retrying-page-reclaim mm/page_alloc.c --- a/mm/page_alloc.c~mm-remove-unnecessary-back-off-function-when-retrying-page-reclaim +++ a/mm/page_alloc.c @@ -3515,11 +3515,10 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_ma /* * Checks whether it makes sense to retry the reclaim to make a forward progress * for the given allocation request. - * The reclaim feedback represented by did_some_progress (any progress during - * the last reclaim round) and no_progress_loops (number of reclaim rounds without - * any progress in a row) is considered as well as the reclaimable pages on the - * applicable zone list (with a backoff mechanism which is a function of - * no_progress_loops). + * + * We give up when we either have tried MAX_RECLAIM_RETRIES in a row + * without success, or when we couldn't even meet the watermark if we + * reclaimed all remaining pages on the LRU lists. * * Returns true if a retry is viable or false to enter the oom path. */ @@ -3564,13 +3563,11 @@ should_reclaim_retry(gfp_t gfp_mask, uns bool wmark; available = reclaimable = zone_reclaimable_pages(zone); - available -= DIV_ROUND_UP((*no_progress_loops) * available, - MAX_RECLAIM_RETRIES); available += zone_page_state_snapshot(zone, NR_FREE_PAGES); /* - * Would the allocation succeed if we reclaimed the whole - * available? + * Would the allocation succeed if we reclaimed all + * reclaimable pages? */ wmark = __zone_watermark_ok(zone, order, min_wmark, ac_classzone_idx(ac), alloc_flags, available); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
