[Bug 81682] New: Frequent framerate drops on i915 chip

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81682

          Priority: medium
            Bug ID: 81682
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: Frequent framerate drops on i915 chip
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: bugsfreedesktop at emeraldreverie.org
          Hardware: Other
            Status: NEW
           Version: XOrg CVS
         Component: DRM/Intel
           Product: DRI

This was originally reported as #81402 but I've realized that I conflated two
issues, and the logs I attached were for a separate issue. Thus I'm separately
raising my core issue for further debugging.

I get intermittent FPS drops on the intel GPU on my laptop, usually every
5-15mins while gaming, during the whole window manager is very slow. This lasts
up to a minute before generally returning to normal. Even low-intensity games
like Faster Than Light etc will trigger it, although it seems to take less time
to trigger with more demanding use (e.g. FTL took nearly 2 hours to trigger it,
while running something like Anomaly Defenders took less than an hour, and Path
of Exile (via wine and the bumblebee-enabled nVidia card) can trigger it in
less than 10 mins).

Hardware: Dell L702x laptop with i915 chip. Lspci -v reports:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core
Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA
controller])
    Subsystem: Dell Device 0571

OS is Archlinux 64bit, running mesa 10.2.4-1 and xf86-video-intel-git
2.99.914-1, although similar behaviour was seen on xf86-video-intel 2.99.912-2.

The trouble I'm having is figuring out what's causing it. Nothing is logged to
/sys/kernel/debug/dri/0/i915_error_state, dmesg, syslog or Xorg.0.log. I can
see no unusual processes running in htop, and I can reproduce it with cron
disabled, so it's not something firing up in the background. Temperature
according to lm_sensors doesn't seem different when the issue is or isn't
happening.

I'm totally at a loss as to how to debug the issue further, so any pointers are
*gratefully* welcomed, since I've been trying to track this issue down for the
better part of 4 months. I'm available on Freenode (in #intel-gfx as
'gwmngilfen') if any real-time debugging can be done.

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