----- Original Message ----- From: Michal Hocko <mhocko@xxxxxxx> To: Felipe Contreras <felipe.contreras@xxxxxxxxx> Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Mel Gorman <mgorman@xxxxxxx>, KAMEZAWA Hiroyuki <kamezawa.hiro Subject: Re: Interactivity regression since v3.11 in mm/vmscan.c Date: 2014-06-06 17:16 On Thu 05-06-14 09:00:10, Felipe Contreras wrote: > On Thu, Jun 5, 2014 at 8:37 AM, Michal Hocko <mhocko@xxxxxxx> wrote: > > On Thu 05-06-14 06:33:40, Felipe Contreras wrote: > > >> 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. > > Well, it's a USB 3.0 device, I can write at 250 MB/s, so it's not > really that slow. > > And in fact, when I read and write to and from the same USB 3.0 > device, I don't see the issue. > > >> 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); > > } > > Unfortunately that doesn't fix the issue for me. >That is really interesting. So removing the test completely helps but >reducing it to kswapd doesn't. I would expect stalls coming from direct >reclaimers not the kswapd. >Mel has a nice systemtap script (attached) to watch for stalls. Maybe >you can give it a try? > Alternatively can we try wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10) ? Hillf?韬{.n?壏?檩jg??a旃??迻)钋?韰骅w+h櫒璀?y/i?⒏?婃⒎?湼Щ烚m???)钋?痂燐^櫒?觥櫒ザ?v夗﨣趓O璁?f?i?⒏?