From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Subject: mm/page_alloc: drain the requested list first during bulk free Prior to the series, pindex 0 (order-0 MIGRATE_UNMOVABLE) was always skipped first and the precise reason is forgotten. A potential reason may have been to artificially preserve MIGRATE_UNMOVABLE but there is no reason why that would be optimal as it depends on the workload. The more likely reason is that it was less complicated to do a pre-increment instead of a post-increment in terms of overall code flow. As free_pcppages_bulk() now typically receives the pindex of the PCP list that exceeded high, always start draining that list. Link: https://lkml.kernel.org/r/20220217002227.5739-5-mgorman@xxxxxxxxxxxxxxxxxxx Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Tested-by: Aaron Lu <aaron.lu@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/mm/page_alloc.c~mm-page_alloc-drain-the-requested-list-first-during-bulk-free +++ a/mm/page_alloc.c @@ -1460,6 +1460,10 @@ static void free_pcppages_bulk(struct zo * below while (list_empty(list)) loop. */ count = min(pcp->count, count); + + /* Ensure requested pindex is drained first. */ + pindex = pindex - 1; + while (count > 0) { struct list_head *list; int nr_pages; _
