Merge lp:~vanvugt/mir/fix-1640366 into lp:mir

[Daniel van Vugt]

Accommodate scheduling issues on slow/loaded machines that could cause
the frame dropping test to occasionally miss a frame. Use the average
rather than worst case in order to ignore such glitches (LP: #1640366)

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3795
https://mir-jenkins.ubuntu.com/job/mir-ci/2132/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/2758
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/2821
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/2813
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/2813
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/2813
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2787/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2787/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2787/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/2787/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2787/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2787
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2787/artifact/output/*zip*/output.zip

Click here to trigger a rebuild:
https://mir-jenkins.ubuntu.com/job/mir-ci/2132/rebuild

review: Approve (continuous-integration)

[Chris Halse Rogers (raof)]

This seems like a significant weakening of the test, but I guess.

We'll need to bite the bullet and do a proper faketime harness for our acceptance tests at some point. We've a bunch of these tests that spuriously fail on loaded machines that we “fix” by not testing the same property.

review: Approve

[Daniel van Vugt (vanvugt)]

This change is not such a big concern to weakening the test. This test exists to verify we don't accidentally implement dropping incorrectly /again/, which would make the latency above 1.0 frames.

[Kevin DuBois (kdub)]

> This seems like a significant weakening of the test, but I guess.
>
> We'll need to bite the bullet and do a proper faketime harness for our
> acceptance tests at some point. We've a bunch of these tests that spuriously
> fail on loaded machines that we “fix” by not testing the same property.

+1, and then no more timing-dependent tests. mp is alright by me as a stopgap in the meantime though.

review: Approve

=== modified file 'tests/acceptance-tests/test_latency.cpp'
--- tests/acceptance-tests/test_latency.cpp	2016-11-09 05:24:36 +0000
+++ tests/acceptance-tests/test_latency.cpp	2016-11-09 05:24:36 +0000
@@ -346,8 +346,8 @@
         mir_buffer_stream_swap_buffers_sync(stream);
     } while (!stats.wait_for_posts(test_submissions, std::chrono::seconds(0)));
 
-    auto max_latency = display.group.max_latency();
-    EXPECT_THAT(max_latency, Lt(0.5f));
+    auto average_latency = display.group.average_latency();
+    EXPECT_THAT(average_latency, Lt(0.5f));
 
     if (server.get_options()->get<bool>(mtd::logging_opt))
         display.group.dump_latency();