Bug 1602907 - Add thread priority and affinity code for non-Windows r=jrmuizel

pthread priority and affinity for Linux; moved to a helper function

Differential Revision: https://phabricator.services.mozilla.com/D56782

--HG--
extra : moz-landing-system : lando

Cargo.lock

@@ -4468,6 +4468,7 @@ dependencies = [
  "foreign-types 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "fxhash 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "gleam 0.6.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.59 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "nsstring 0.1.0",
  "num_cpus 1.7.0 (registry+https://github.com/rust-lang/crates.io-index)",

gfx/webrender_bindings/Cargo.toml

@@ -31,6 +31,9 @@ dwrote = "0.9"
 dirs = "1.0"
 winapi = "0.3"
 
+[target.'cfg(target_os = "linux")'.dependencies]
+libc = "0.2"
+
 [target.'cfg(target_os = "macos")'.dependencies]
 core-foundation = "0.6"
 core-graphics = "0.17.1"

gfx/webrender_bindings/src/bindings.rs

@@ -42,7 +42,12 @@ use rayon;
 use num_cpus;
 use euclid::SideOffsets2D;
 use nsstring::nsAString;
-//linux only//use thread_priority::*;
+
+#[cfg(target_os = "linux")]
+use libc::{
+    pthread_self, pthread_setschedparam, sched_param,
+    cpu_set_t, CPU_SET, pthread_setaffinity_np
+};
 
 #[cfg(target_os = "macos")]
 use core_foundation::string::CFString;
@@ -1066,12 +1071,14 @@ pub unsafe extern "C" fn wr_thread_pool_new(low_priority: bool) -> *mut WrThread
 
     let priority_tag = if low_priority { "LP" } else { "" };
 
-    let worker = rayon::ThreadPoolBuilder::new()
-        .thread_name(move |idx|{ format!("WRWorker{}#{}", priority_tag, idx) })
-        .num_threads(num_threads)
-        .start_handler(move |idx| {
+    // helper function to make sure that low priority threads really are low priority.
+    // it also sets the affinity so that WRWorkerX and WRWorkerLPX are both locked to
+    // the same core X, so one or the other can run, but not both: the total number
+    // of worker threads that's running should respect num_threads above, even if
+    // they exist in two separate pools.
     #[cfg(target_os = "windows")]
-            {
+    fn set_thread_priority_and_affinity(low_priority:bool, thread_index: usize) {
+        unsafe {
             SetThreadPriority(
                 GetCurrentThread(),
                 if low_priority {
@@ -1079,12 +1086,32 @@ pub unsafe extern "C" fn wr_thread_pool_new(low_priority: bool) -> *mut WrThread
                 } else {
                     0 /* THREAD_PRIORITY_NORMAL */
                 });
-                SetThreadAffinityMask(GetCurrentThread(), 1usize << idx);
+            SetThreadAffinityMask(GetCurrentThread(), 1usize << thread_index);
         }
-            /*let thread_id = thread_native_id();
-            set_thread_priority(thread_id,
-                if low_priority { ThreadPriority::Min } else { ThreadPriority::Max },
-                ThreadSchedulePolicy::Normal(NormalThreadSchedulePolicy::Normal));*/
+    }
+    #[cfg(target_os = "linux")]
+    fn set_thread_priority_and_affinity(low_priority:bool, thread_index: usize) {
+        unsafe {
+            let thread_id = pthread_self();
+            if low_priority {
+                let params = sched_param {
+                    sched_priority: 0
+                };
+                pthread_setschedparam(thread_id, 3 /* SCHED_BATCH */, &params);
+            }
+            let mut cpu_set = mem::zeroed::<cpu_set_t>();
+            CPU_SET(thread_index, &mut cpu_set);
+            pthread_setaffinity_np(thread_id, mem::size_of::<cpu_set_t>(), &cpu_set);
+        }
+    }
+    #[cfg(not(any(target_os = "windows", target_os = "linux" )))]
+    fn set_thread_priority_and_affinity(_low_priority:bool, _thread_index: usize) { }
+
+    let worker = rayon::ThreadPoolBuilder::new()
+        .thread_name(move |idx|{ format!("WRWorker{}#{}", priority_tag, idx) })
+        .num_threads(num_threads)
+        .start_handler(move |idx| {
+            set_thread_priority_and_affinity(low_priority, idx);
             wr_register_thread_local_arena();
             let name = format!("WRWorker{}#{}",priority_tag, idx);
             register_thread_with_profiler(name.clone());

gfx/webrender_bindings/src/lib.rs

@@ -23,7 +23,8 @@ extern crate log;
 extern crate dwrote;
 #[cfg(target_os = "windows")]
 extern crate winapi;
-
+#[cfg(target_os = "linux")]
+extern crate libc;
 
 #[cfg(target_os = "macos")]
 extern crate core_foundation;