On 2/17/22 01:22, Mel Gorman wrote:
> free_pcppages_bulk() frees pages in a round-robin fashion. Originally,
> this was dealing only with migratetypes but storing high-order pages
> means that there can be many more empty lists that are uselessly
> checked. Track the minimum and maximum active pindex to reduce the
> search space.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/page_alloc.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 08de32cfd9bb..85cc1fe8bcc5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1450,6 +1450,8 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> struct per_cpu_pages *pcp)
> {
> int pindex = 0;
> + int min_pindex = 0;
> + int max_pindex = NR_PCP_LISTS - 1;
> int batch_free = 0;
> int nr_freed = 0;
> unsigned int order;
> @@ -1475,13 +1477,20 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> */
> do {
> batch_free++;
> - if (++pindex == NR_PCP_LISTS)
> - pindex = 0;
> + if (++pindex > max_pindex)
> + pindex = min_pindex;
> list = &pcp->lists[pindex];
> - } while (list_empty(list));
> + if (!list_empty(list))
> + break;
> +
> + if (pindex == max_pindex)
> + max_pindex--;
> + if (pindex == min_pindex)
> + min_pindex++;
> + } while (1);
>
> /* This is the only non-empty list. Free them all. */
> - if (batch_free == NR_PCP_LISTS)
> + if (batch_free >= max_pindex - min_pindex)
> batch_free = count;
>
> order = pindex_to_order(pindex);
