On Sat, 14 Jan 2012, Hillf Danton wrote:
>
> When shrinking inactive lru list, isolated pages are queued on locally private
> list, so the lock-hold time could be reduced if pages are counted without lock
> protection. To achive that, firstly updating reclaim stat is delayed until the
> putback stage, which is pointed out by Hugh, after reacquiring the lru lock.
>
> Secondly operations related to vm and zone stats, are now proteced with
> preemption disabled as they are per-cpu operation.
>
> Thanks for comments and ideas received.
>
>
> Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
Thank you, I like this a lot: it undoes a little of the cleanup I just
did, but for much better reason than I had. I'm running with it now.
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
>
> --- a/mm/vmscan.c Sat Jan 14 14:02:20 2012
> +++ b/mm/vmscan.c Sat Jan 14 20:00:46 2012
> @@ -1414,7 +1414,6 @@ update_isolated_counts(struct mem_cgroup
> unsigned long *nr_anon,
> unsigned long *nr_file)
> {
> - struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
> struct zone *zone = mz->zone;
> unsigned int count[NR_LRU_LISTS] = { 0, };
> unsigned long nr_active = 0;
> @@ -1435,6 +1434,7 @@ update_isolated_counts(struct mem_cgroup
> count[lru] += numpages;
> }
>
> + preempt_disable();
> __count_vm_events(PGDEACTIVATE, nr_active);
>
> __mod_zone_page_state(zone, NR_ACTIVE_FILE,
> @@ -1449,8 +1449,9 @@ update_isolated_counts(struct mem_cgroup
> *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
>
> - reclaim_stat->recent_scanned[0] += *nr_anon;
> - reclaim_stat->recent_scanned[1] += *nr_file;
> + __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
> + __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
> + preempt_enable();
> }
>
> /*
> @@ -1512,6 +1513,7 @@ shrink_inactive_list(unsigned long nr_to
> unsigned long nr_writeback = 0;
> isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
> struct zone *zone = mz->zone;
> + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
>
> while (unlikely(too_many_isolated(zone, file, sc))) {
> congestion_wait(BLK_RW_ASYNC, HZ/10);
> @@ -1546,19 +1548,13 @@ shrink_inactive_list(unsigned long nr_to
> __count_zone_vm_events(PGSCAN_DIRECT, zone,
> nr_scanned);
> }
> + spin_unlock_irq(&zone->lru_lock);
>
> - if (nr_taken == 0) {
> - spin_unlock_irq(&zone->lru_lock);
> + if (nr_taken == 0)
> return 0;
> - }
>
> update_isolated_counts(mz, &page_list, &nr_anon, &nr_file);
>
> - __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
> - __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
> -
> - spin_unlock_irq(&zone->lru_lock);
> -
> nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
> &nr_dirty, &nr_writeback);
>
> @@ -1570,6 +1566,9 @@ shrink_inactive_list(unsigned long nr_to
> }
>
> spin_lock_irq(&zone->lru_lock);
> +
> + reclaim_stat->recent_scanned[0] += nr_anon;
> + reclaim_stat->recent_scanned[1] += nr_file;
>
> if (current_is_kswapd())
> __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
--
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