Bug 109055 - ~10% perf drop in Sascha Willems Vulkan Multithreading demo
Summary: ~10% perf drop in Sascha Willems Vulkan Multithreading demo
Status: NEW
Alias: None
Product: Mesa
Classification: Unclassified
Component: Drivers/Vulkan/intel (show other bugs)
Version: git
Hardware: Other All
: medium normal
Assignee: Intel 3D Bugs Mailing List
QA Contact: Intel 3D Bugs Mailing List
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Reported: 2018-12-13 18:06 UTC by Eero Tamminen
Modified: 2019-01-11 15:32 UTC (History)
1 user (show)

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Description Eero Tamminen 2018-12-13 18:06:58 UTC
Setup:
* SKL or KBL device (don't have data from others)
* Ubuntu 18.04 / Unity
* drm-tip v4.19 or newer kernel
* git version of X with modifiers (dmabuf capable) enabled
* Mesa git version

Test-case:
* multithreading --fullscreen --benchmark --benchwarmup 3 --benchruntime 20

Result:
* FPS drops by 5-10%

Between following Mesa commits:
41c8f991379d1a 2018-11-12 18:28:04 util: Fix warning in u_cpu_detect on non-x86
25b48e3df93dee 2018-11-14 12:12:09 st/xa: Bump minor

Along with the perf drop, one can see both CPU & GPU power usage drops (according to RAPL), and GPU spending 30-40% in RC6 instead of 0%.

I.e. there's a Mesa change that makes this GPU test CPU bound.

I didn't see any significant perf changes in other benchmarks (Vulkan or GL).
Comment 1 Eero Tamminen 2019-01-11 15:32:20 UTC
There was some change between following commits:
* 2018-12-31 19:52:08 8c93ef5de9: radv: Do a cache flush if needed before reading predicates.
* 2019-01-02 18:09:04 7d6babf995: nir: add a way to print the deref chain

That changed the multithreading test perf:
* Fixed half of KBL-7 GT2 regression
* Fixed half of combined perf regression for SKL-i5 GT2, for the indicated interval, and another (as large) regression at end of November
* Improved perf a lot on BDW-3 GT2, much more than the small regression

GPU still spends significant time in RC6 (~20% on BDW-i3, 35-40% on SKL-i5, 45% on KBL-i7).  CPU vs GPU power usage changes differ between platforms, but they're fairly small.  All in all, pretty nice with clearly increased perf.


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