Merge lp:~vanvugt/mir/testfix-1211700 into lp:mir

[Daniel van Vugt]

Experimental test fix to work around drivers that lack adequate GPU
load balancing (LP: #1211700, LP: #1665802)

On radeon at least, this provides 10-400x improvement in compositor
performance (with an interval 0 client hogging the GPU), making the system usable:

radeon:
before: 0.05 FPS - 2 FPS
after: 20 FPS

nouveau:
before: 6 FPS
after: 6 FPS

freedreno (Alberto?):
before: ?
after: ?

[Daniel van Vugt (vanvugt)]

For testing only.

review: Disapprove

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

FAILED: Continuous integration, rev:4078
https://mir-jenkins.ubuntu.com/job/mir-ci/3119/
Executed test runs:
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-mir/4187/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/4274
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/4264
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/4264
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=zesty/4264
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=zesty/4214/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/4214/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=zesty/4214/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/4214/console
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/4214/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/4214
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/4214/artifact/output/*zip*/output.zip
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/4214/console

Click here to trigger a rebuild:
https://mir-jenkins.ubuntu.com/job/mir-ci/3119/rebuild

review: Needs Fixing (continuous-integration)

Unmerged revisions

4078. By Daniel van Vugt on 2017-03-09

Rewrite the load balancing against latest trunk

=== modified file 'src/server/compositor/multi_threaded_compositor.cpp'
--- src/server/compositor/multi_threaded_compositor.cpp	2017-01-20 12:32:45 +0000
+++ src/server/compositor/multi_threaded_compositor.cpp	2017-03-09 09:52:49 +0000
@@ -32,6 +32,7 @@
 #include "mir/unwind_helpers.h"
 #include "mir/thread_name.h"
 
+#include <shared_mutex>
 #include <thread>
 #include <chrono>
 #include <condition_variable>
@@ -48,6 +49,8 @@
 namespace compositor
 {
 
+extern std::shared_timed_mutex gpu_load_balance;
+
 class CompositingFunctor
 {
 public:
@@ -113,6 +116,7 @@
         try
         {
             std::unique_lock<std::mutex> lock{run_mutex};
+            std::shared_lock<std::shared_timed_mutex> throttle(gpu_load_balance);
             while (running)
             {
                 /* Wait until compositing has been scheduled or we are stopped */
@@ -140,6 +144,11 @@
                         auto& compositor = std::get<1>(tuple);
                         compositor->composite(scene->scene_elements_for(compositor.get()));
                     }
+
+                    // Only allow unthrottled clients to saturate the GPU during
+                    // page flipping where we're basically idle waiting for
+                    // vblank...
+                    throttle.unlock();
                     group.post();
 
                     /*
@@ -153,6 +162,7 @@
                                  force_sleep : group.recommended_sleep();
                     std::this_thread::sleep_for(delay);
 
+                    throttle.lock();
                     lock.lock();
 
                     /*

=== modified file 'src/server/compositor/stream.cpp'
--- src/server/compositor/stream.cpp	2017-03-08 19:29:37 +0000
+++ src/server/compositor/stream.cpp	2017-03-09 09:52:49 +0000
@@ -26,6 +26,7 @@
 #include "mir/compositor/frame_dropping_policy_factory.h"
 #include "mir/compositor/frame_dropping_policy.h"
 #include <boost/throw_exception.hpp>
+#include <shared_mutex>
 
 namespace mc = mir::compositor;
 namespace geom = mir::geometry;
@@ -33,6 +34,10 @@
 namespace ms = mir::scene;
 namespace geom = mir::geometry;
 
+namespace mir { namespace compositor {
+    std::shared_timed_mutex gpu_load_balance;
+} } // namespace mir::compositor
+
 enum class mc::Stream::ScheduleMode {
     Queueing,
     Dropping
@@ -109,7 +114,9 @@
     // IO. Holding it locked blocks the compositor thread(s) from rendering.
     if (deferred_io.valid())
     {
-        // TODO: Throttling of GPU hogs goes here (LP: #1211700, LP: #1665802)
+        // Throttle GPU hogs such that they can only saturate the GPU while
+        // no compositors are needing it (LP: #1211700, LP: #1665802)
+        { std::unique_lock<std::shared_timed_mutex> lock(gpu_load_balance); }
         deferred_io.wait();
     }
 }