diff options
| -rw-r--r-- | mm/vmscan.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 53e4534885ad..5a8776eb0f43 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1439,6 +1439,19 @@ putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) } /* + * If a kernel thread (such as nfsd for loop-back mounts) services + * a backing device by writing to the page cache it sets PF_LESS_THROTTLE. + * In that case we should only throttle if the backing device it is + * writing to is congested. In other cases it is safe to throttle. + */ +static int current_may_throttle(void) +{ + return !(current->flags & PF_LESS_THROTTLE) || + current->backing_dev_info == NULL || + bdi_write_congested(current->backing_dev_info); +} + +/* * shrink_inactive_list() is a helper for shrink_zone(). It returns the number * of reclaimed pages */ @@ -1566,7 +1579,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * implies that pages are cycling through the LRU faster than * they are written so also forcibly stall. */ - if (nr_unqueued_dirty == nr_taken || nr_immediate) + if ((nr_unqueued_dirty == nr_taken || nr_immediate) && + current_may_throttle()) congestion_wait(BLK_RW_ASYNC, HZ/10); } @@ -1575,7 +1589,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * is congested. Allow kswapd to continue until it starts encountering * unqueued dirty pages or cycling through the LRU too quickly. */ - if (!sc->hibernation_mode && !current_is_kswapd()) + if (!sc->hibernation_mode && !current_is_kswapd() && + current_may_throttle()) wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |