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Hi all,
I recently updated Arch in a long while (the last system update was at 2015-12-16). The most annoying issue, and one I haven't been able to resolve after perusing the forums thoroughly, is that once in a while (several times per minute) there is a short system stutter or lag (lasting for less than a second, but clearly noticable). Everything seems to be affected by the lag, e.g. the mouse cursor and video playback. When a video is playing in VLC, frames are dropped at the same time as the mouse cursor hangs when moving it around. The machine is a HP laptop with an Intel chipset and graphics, running XFCE.
I have tried the following suggestions from previous threads on the forums, none of which have helped:
Running the LTS kernel
Uninstalled the xf86-video-intel driver and used the modesetting driver instead
Turning compositing on and off (the XFCE compositor and xcompmgr)
Grasped at various straws like removing sensor interface packages (lm_sensors) and turning vsync on / off
The journal and dmesg don't have any interesting output at the time of the lags. Full dmesg output is here. One thing that catches my eye are the warnings about SysemIO and OpRegion conflicts, but I'm not sure what to make of that.
Any help is appreciated.
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An update on the investigation. Since I noticed that audio doesn't stutter (but video, mouse / keyboard input does), I reckoned this has something to do with the graphics driver or X. I ran an strace on glxgears (which also exhibits the stutter):
strace -r glxgears -geometry 500x500 2>&1 >/dev/null | tee glxtrace2Sorting the output numerically decreasing shows that some recvmsg syscalls take a very long time, definitely enough to cause a detectable lag. Lines such as this are present in the output for every lag event:
0.000053 poll([{fd=3, events=POLLIN}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
0.237675 recvmsg(3, {msg_name(0)=NULL, msg_iov(1)=[{"f\0f\34\2\0\0\0\2\0 \3\1\0\0\0\320\0r\214\0\0\0\0\216\v\0\0j\t\0\0", 4096}], msg_controllen=0, msg_flags=0}, 0) = 32File descriptor 3 is the X11 socket:
0.000118 socket(AF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0) = 3
0.000053 connect(3, {sa_family=AF_LOCAL, sun_path=@"/tmp/.X11-unix/X0"}, 20) = 0So for some reason glxgears (and presumably other apps) has to wait almost a quarter of a second on X11 a couple of times per minute. No idea why.
Last edited by frukt (2016-07-19 19:47:08)
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My current workaround is downgrading the kernel to 4.2.5, so I'm pretty sure the issue is with the i915 kernel driver.
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