On 03/01/2018 07:28 AM, Aaron Lu wrote:
> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
>
> No functionality or performance change is expected from this patch.
Well, it's N decrements instead of one decrement by N / assignment of
zero. But I assume the difference is negligible anyway, right?
> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/page_alloc.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..faa33eac1635 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> page = list_last_entry(list, struct page, lru);
> /* must delete as __free_one_page list manipulates */
> list_del(&page->lru);
> + pcp->count--;
>
> mt = get_pcppage_migratetype(page);
> /* MIGRATE_ISOLATE page should not go to pcplists */
> @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
> local_irq_save(flags);
> batch = READ_ONCE(pcp->batch);
> to_drain = min(pcp->count, batch);
> - if (to_drain > 0) {
> + if (to_drain > 0)
> free_pcppages_bulk(zone, to_drain, pcp);
> - pcp->count -= to_drain;
> - }
> local_irq_restore(flags);
> }
> #endif
> @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone)
> pset = per_cpu_ptr(zone->pageset, cpu);
>
> pcp = &pset->pcp;
> - if (pcp->count) {
> + if (pcp->count)
> free_pcppages_bulk(zone, pcp->count, pcp);
> - pcp->count = 0;
> - }
> local_irq_restore(flags);
> }
>
> @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn)
> if (pcp->count >= pcp->high) {
> unsigned long batch = READ_ONCE(pcp->batch);
> free_pcppages_bulk(zone, batch, pcp);
> - pcp->count -= batch;
> }
> }
>
>
