Bug 46834 - small performance when playing flightgear (swrast fallback through GTT mapping)
Summary: small performance when playing flightgear (swrast fallback through GTT mapping)
Alias: None
Product: Mesa
Classification: Unclassified
Component: Drivers/DRI/i965 (show other bugs)
Version: git
Hardware: x86-64 (AMD64) Linux (All)
: medium normal
Assignee: Kenneth Graunke
QA Contact:
Depends on:
Reported: 2012-03-01 08:59 UTC by Jan Kundrát
Modified: 2012-05-04 17:21 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:


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Description Jan Kundrát 2012-03-01 08:59:40 UTC
Running flightgear 2.4.0 on my machine leads to roughly 1 FPS rendering. When I run the same command, but with LIBGL_ALWAYS_SOFTWARE=1, I get around 15 FPS.

ickle on IRC suggested that:

17:47 < ickle> jkt: that would imply that the driver is falling back to swrast, only it does so an GTT mapping which is much slower than regular memory

He also mentioned that one could fix this issue by lots of beer and that I shall talk to a gentleman called Kayden -- and that's what I'm doing now.

64bit Gentoo Linux, Thinkpad T420s
"2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)"
xf86-video-intel: 3c4f29820bca336af2c997bafc7ef288b455813c (using SNA)
libdrm: 783db34f6d8aded019b005a957fed1b91fd67c7c
mesa: 6b024464e80d035fe92c9c15761a0ac269a8ad51

Just tell me if you need more information.
Comment 1 Kenneth Graunke 2012-05-04 17:21:05 UTC
Sorry this took so long.  Fixed in Mesa master with:

commit 3cd7bee48f7caf7850ea64d40f43875d4c975507
Author: Kenneth Graunke <kenneth@whitecape.org>
Date:   Mon Mar 5 13:54:29 2012 -0800

    intel: Remove pointless software fallback for glBitmap on Gen6.
    We already have a meta path below that works just fine; no apparent
    regressions in oglconform.
    NOTE: This is a candidate for the 8.0 branch.
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=46834
    Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

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