On Wed, 14 Sep 2022 10:33:18 +0800 Hongchen Zhang <zhanghongchen@xxxxxxxxxxx> wrote: > when a process falls into page fault and there is not enough free > memory,it will do direct reclaim. At the same time,it is holding > mmap_lock.So in case of multi-thread,it should exit from page fault > ASAP. > When reclaim memory,we do scan adjust between anon and file lru which > may cost too much time and trigger hung task for other thread.So for a > process which is not kswapd,it should just do a little scan adjust. Well, that's a pretty nasty bug. Before diving into a possible fix, can you please tell us more about how this happens? What sort of machine, what sort of workload. Can you suggest why others are not experiencing this? > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3042,11 +3042,17 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > nr[lru] = targets[lru] * (100 - percentage) / 100; > nr[lru] -= min(nr[lru], nr_scanned); > > + if (!current_is_kswapd()) > + nr[lru] = min(nr[lru], nr_to_reclaim); > + > lru += LRU_ACTIVE; > nr_scanned = targets[lru] - nr[lru]; > nr[lru] = targets[lru] * (100 - percentage) / 100; > nr[lru] -= min(nr[lru], nr_scanned); > > + if (!current_is_kswapd()) > + nr[lru] = min(nr[lru], nr_to_reclaim); > + > scan_adjusted = true; > } > blk_finish_plug(&plug); It would be better if these additions had code comments explaining why they're there. But let's more fully understand the problem before altering your patch.
