Details
-
Bug
-
Resolution: Invalid
-
P1: Critical
-
None
-
5.11, 5.12
-
None
-
Slackware 32bit-current, with X run as root
-
Linux/X11
Description
I suspect I have a pretty peculiar environment, since this regression is quite noticeable for me but nobody else seems to be affected.
Anyway, commit 24adaa9a742e6f95ff897d0eb9a2bce0527dd042 (xcb: Fix access to shm for X server running from another user) made qt5 unusable on my system (Slackware 32bit-current, with X run as root). After this commit, pretty much any qt5 application seems to access the disk at any user interaction, slowing everything down massively (rusty old HD here). However, 'top' does not show anything unusual: 'iostat' does.
Here's an example running qgit (https://github.com/tibirna/qgit). I'm just opening and then immediately closing the application. With qt 5.9, it starts in less than a second and closes immediately; with qt 5.12 it starts in about 15 seconds and closes in about 5 seconds (more if something else is using the disk).
With qt 5.9:
$ iostat -y 1 -z -s -h
avg-cpu: %user %nice %system %iowait %steal %idle
0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
avg-cpu: %user %nice %system %iowait %steal %idle
2.6% 0.0% 0.8% 1.5% 0.0% 95.2%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
14.00 0.0k 320.0k 0.0k 320.0k sda
avg-cpu: %user %nice %system %iowait %steal %idle
1.1% 0.0% 0.3% 0.9% 0.0% 97.7%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
7.00 0.0k 208.0k 0.0k 208.0k sda
avg-cpu: %user %nice %system %iowait %steal %idle
2.8% 0.0% 0.7% 0.0% 0.0% 96.6%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
avg-cpu: %user %nice %system %iowait %steal %idle
2.7% 0.0% 1.0% 1.8% 0.0% 94.6%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
26.00 0.0k 272.0k 0.0k 272.0k sda
With qt 5.12:
$ iostat -y 1 -z -s -h
avg-cpu: %user %nice %system %iowait %steal %idle
0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
avg-cpu: %user %nice %system %iowait %steal %idle
1.0% 0.0% 0.2% 0.0% 0.0% 98.8%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
avg-cpu: %user %nice %system %iowait %steal %idle
2.7% 0.0% 0.9% 6.0% 0.0% 90.4%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
310.00 0.0k 2.5M 0.0k 2.5M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.2% 8.3% 0.0% 90.7%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
524.00 0.0k 8.8M 0.0k 8.8M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.4% 7.9% 0.0% 90.9%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
583.00 0.0k 12.9M 0.0k 12.9M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.1% 8.2% 0.0% 90.9%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
518.00 0.0k 4.3M 0.0k 4.3M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.3% 8.2% 0.0% 90.8%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
524.00 0.0k 3.7M 0.0k 3.7M sda
avg-cpu: %user %nice %system %iowait %steal %idle
1.1% 0.0% 0.2% 8.5% 0.0% 90.2%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
436.00 0.0k 2.7M 0.0k 2.7M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.3% 8.3% 0.0% 90.7%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
498.00 0.0k 2.4M 0.0k 2.4M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.7% 0.0% 0.2% 8.2% 0.0% 91.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
592.00 0.0k 9.2M 0.0k 9.2M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.2% 8.3% 0.0% 90.7%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
507.00 0.0k 2.4M 0.0k 2.4M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.3% 8.2% 0.0% 90.8%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
536.00 0.0k 4.0M 0.0k 4.0M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.1% 8.6% 0.0% 90.5%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
487.00 0.0k 2.6M 0.0k 2.6M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.2% 9.2% 0.0% 89.9%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
575.00 0.0k 3.9M 0.0k 3.9M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.2% 8.2% 0.0% 91.1%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
565.00 0.0k 8.6M 0.0k 8.6M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.7% 0.0% 0.2% 8.2% 0.0% 91.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
505.00 0.0k 2.5M 0.0k 2.5M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.3% 8.1% 0.0% 90.9%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
544.00 0.0k 5.1M 0.0k 5.1M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.1% 8.6% 0.0% 90.7%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
501.00 0.0k 3.0M 0.0k 3.0M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.2% 8.2% 0.0% 91.1%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
540.00 0.0k 4.5M 0.0k 4.5M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.7% 0.0% 0.2% 8.1% 0.0% 91.1%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
546.00 0.0k 9.7M 0.0k 9.7M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.5% 0.0% 0.1% 8.2% 0.0% 91.2%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
496.00 0.0k 2.0M 0.0k 2.0M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.3% 8.0% 0.0% 91.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
584.00 0.0k 8.4M 0.0k 8.4M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.2% 8.1% 0.0% 91.1%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
552.00 0.0k 6.2M 0.0k 6.2M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.8% 0.0% 0.1% 8.2% 0.0% 91.0%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
582.00 0.0k 8.7M 0.0k 8.7M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.2% 8.6% 0.0% 90.6%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
556.00 0.0k 6.6M 0.0k 6.6M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.6% 0.0% 0.1% 8.1% 0.0% 91.2%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
598.00 0.0k 8.2M 0.0k 8.2M sda
avg-cpu: %user %nice %system %iowait %steal %idle
2.1% 0.0% 0.3% 8.0% 0.0% 89.6%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
508.00 0.0k 3.8M 0.0k 3.8M sda
avg-cpu: %user %nice %system %iowait %steal %idle
0.7% 0.0% 0.3% 8.2% 0.0% 90.9%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
737.00 0.0k 18.1M 0.0k 18.1M sda
avg-cpu: %user %nice %system %iowait %steal %idle
1.8% 0.0% 0.4% 3.6% 0.0% 94.1%
tps kB_read/s kB_w+d/s kB_read kB_w+d Device
87.00 0.0k 2.0M 0.0k 2.0M sda
I.e. tens of accesses to disk vs tens of tousands.
I've verified that simply commenting the line
#define XCB_USE_SHM_FD
in src/plugins/platforms/xcb/qxcbbackingstore.cpp on top of v5.12.4 fixes the issue on my system.
Now I'm not sure if my environment is somewhat messed up (any hint?), but it doesn't seem to have any problem with other libraries or applications.