Ian Armstrong posted on Tue, 02 Dec 2014 18:56:13 +0000 as excerpted: > On Tue, 2 Dec 2014 12:48:21 +0000 (UTC) > Duncan <1i5t5.dun...@cox.net> wrote: > >> FWIW, agreed that it's unlikely to be the drive, especially if you're >> not seeing bus resets or drive errors in dmesg and smart says the drive >> is fine, as I expect it does/will. It may be a btrfs bug or scaling >> issue, of which btrfs still has some, or it could simply be the single >> mode vs raid0 mode issue I explain below. > > I encountered a similar problem here a few days ago on a btrfs raid1 > partition while using rsync to clone a (~30GB) directory. > > Everything started fine, but I came back an hour later to find rsync had > apparently stalled at about 20% with cpu usage at 100% on a single > kworker thread. I was able to kill rsync eventually, and after a while > (don't know how long, but >10 minutes) cpu usage returned to normal. > Restarting rsync resulted in kworker at 100% cpu in less than a minute. > Once stalled there was little drive access happening. Another raid1 > partition (mdadm/ext4) on the same drive pair was having no problems. > Nothing showed in the system logs. > > In this instance I'd forgotten to delete a temporary 500GB file before > starting rsync, so although recently balanced (musage=80/dusage=80) it > was running at near capacity. > > After a reboot, deleting the 500GB file & running balance, everything > returned to normal. Ran rsync again & it completed fine. > > Running slackware current, with Kernel 3.16.4
FWIW that was my point -- there are still such bugs out there, often corner-case so they don't affect most folks most of the time, but out there. I had a similar stall recently, a kworker stuck at 100% that went away after I killed whatever app had triggered the problem (pan, the news program I'm writing this with, as it happens). In my case I chalked it up to a known corner-case bug in my slightly old 3.17.0 kernel (my use- case doesn't do read-only snapshots so I'm not affected by that known bug that effectively blacklists 3.17.0 for some users; this would have been a different one). I don't /know/ it was that bug, but it most likely was, as it's a known but rare corner-case that AFAIK is already fixed in the late 3.18-rcs. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
