On Thu 05-06-14 06:33:40, Felipe Contreras wrote: > Hi, Hi, > For a while I've noticed that my machine bogs down in certain > situations, usually while doing heavy I/O operations, it is not just the > I/O operations, but everything, including the graphical interface, even > the mouse pointer. > > As far as I can recall this did not happen in the past. > > I noticed this specially on certain operations, for example updating a > a game on Steam (to an exteranl USB 3.0 device), or copying TV episodes > to a USB memory stick (probably flash-based). We had a similar report for opensuse. The common part was that there was an IO to a slow USB device going on. > Today I decided to finally hunt down the problem, so I created a > synthetic test that basically consists on copying a bunch of files from > one drive to another (from an SSD to an external USB 3.0). This is > pretty similar to what I noticed; the graphical interface slows down. > > Then I bisected the issue and it turns out that indeed it wasn't > happening in the past, it started happening in v3.11, and it was > triggered by this commit: > > e2be15f (mm: vmscan: stall page reclaim and writeback pages based on > dirty/writepage pages encountered) > > Then I went back to the latest stable version (v3.14.5), and commented > out the line I think is causing the slow down: > > if (nr_unqueued_dirty == nr_taken || nr_immediate) > congestion_wait(BLK_RW_ASYNC, HZ/10); Yes, I came to the same check. I didn't have any confirmation yet so thanks for your confirmation. I've suggested to reduce this congestion_wait only to kswapd: diff --git a/mm/vmscan.c b/mm/vmscan.c index 32c661d66a45..ef6a1c0e788c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1566,7 +1566,7 @@ 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_is_kswapd()) congestion_wait(BLK_RW_ASYNC, HZ/10); } But I am still not sure whether this is the right way to fix it. Direct reclaimers can be throttled later on wait_iff_congested. I guess the original intention was to throttle kswapd to not scan LRU full of dirty pages like crazy. So I think it makes some sense to reduce the congestion_wait only to kswapd. > After that I don't notice the slow down any more. > > Anybody has any ideas how to fix the issue properly? > > -- > Felipe Contreras > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>