Bug#843349: linux-image-4.7.0-1-amd64: Intermittently high system load, sluggish response, no /proc/<pid>/stat utime,stime,etc. reported

[Tom Lee <debian@tomlee.co>]

Also potentially relevant: kworker/0:0 has 421h on-cpu time reported per htop (the TIME+ column) and top. /proc/<pid>/stat output for PID=4 (kworker/0:0) vs PID=63 (kworker/1:1):

tom@desktop ~ $ cat /proc/63/stat

63 (kworker/1:1) S 2 0 0 0 -1 69238880 0 0 0 0 0 0 0 0 20 0 1 0 82 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 0 0 0 17 1 0 0 184 0 0 0 0 0 0 0 0 0 0

tom@desktop ~ $ cat /proc/4/stat

4 (kworker/0:0) S 2 0 0 0 -1 69238880 0 0 0 0 151836336 0 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0

In fact, kworker:0:0 seems to be the only process with on-cpu stats reported (forgive the shell abuse, quick and dirty):

$ for pid in $(ls /proc | awk '/^[0-9]*$/'); do [ -d /proc/$pid ] && awk '$14 != "0" { print $2 }' /proc/$pid/stat; done

(kworker/0:0)

$

On Sun, Nov 20, 2016 at 2:12 PM, Tom Lee <debian@tomlee.co> wrote:

Tried 4.8.0-1 with similar results. Perhaps slightly better, but not much.

$ uname -a

Linux desktop 4.8.0-1-amd64 #1 SMP Debian 4.8.5-1 (2016-10-28) x86_64 GNU/Linux

Like 4.7, can't see what's hogging the CPUs as per-process CPU stats don't appear to be correctly reported in /proc/<pid>/stat.

4.6.x continues to be perfect with respect to both overall performance and the correctness of /proc/<pid>/stat.

On Sat, Nov 12, 2016 at 8:23 PM, Ben Hutchings <ben@decadent.org.uk> wrote:

Control: tag -1 moreinfo

On Sun, 2016-11-06 at 00:02 -0700, Tom Lee wrote:
[...]
> Downgrading to linux-image-4.6.0-1-amd64 fixed all symptoms. Haven't yet
> tried 4.8.0-1 from unstable, not sure if it's impacted.
[...]

Please do.

Ben.

--
Ben Hutchings
Nothing is ever a complete failure; it can always serve as a bad
example.

--

Tom Lee / http://tomlee.co / @tglee

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Tom Lee / http://tomlee.co / @tglee