On 01/04/2017 11:19 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> shrink_page_list returns quite some counters back to its caller. Extract
> the existing 5 into struct reclaim_stat because this makes the code
> easier to follow and also allows further counters to be returned.
>
> While we are at it, make all of them unsigned rather than unsigned long
> as we do not really need full 64b for them (we never scan more than
> SWAP_CLUSTER_MAX pages at once). This should reduce some stack space.
>
> This patch shouldn't introduce any functional change.
[...]
> @@ -1266,11 +1270,13 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> list_splice(&ret_pages, page_list);
> count_vm_events(PGACTIVATE, pgactivate);
>
> - *ret_nr_dirty += nr_dirty;
> - *ret_nr_congested += nr_congested;
> - *ret_nr_unqueued_dirty += nr_unqueued_dirty;
> - *ret_nr_writeback += nr_writeback;
> - *ret_nr_immediate += nr_immediate;
> + if (stat) {
> + stat->nr_dirty = nr_dirty;
> + stat->nr_congested = nr_congested;
> + stat->nr_unqueued_dirty = nr_unqueued_dirty;
> + stat->nr_writeback = nr_writeback;
> + stat->nr_immediate = nr_immediate;
> + }
This change of '+=' to '=' raised my eybrows, but it seems both callers
don't care so this is indeed no functional change and potentially faster.
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