tor-browser

commit c393a4ee5cfffd2882223d2f98c2527ae60f8d0f
parent db8adc0130c65d56868800a68a50c63c77bd5e5e
Author: Paul Bone <paul@bone.id.au>
Date:   Tue, 18 Nov 2025 02:07:23 +0000

Bug 1987055 - pt 2. Merge purge results, ReachedThreshold and Busy r=glandium,profiler-reviewers,mstange

Differential Revision: https://phabricator.services.mozilla.com/D263335

Diffstat:
M
memory/build/mozjemalloc.cpp
 | 
15
++++++++-------
M
memory/build/mozjemalloc_types.h
 | 
9
++++-----
M
tools/profiler/core/memory_markers.cpp
 | 
7
++-----

3 files changed, 14 insertions(+), 17 deletions(-)
diff --git a/memory/build/mozjemalloc.cpp b/memory/build/mozjemalloc.cpp
@@ -1897,7 +1897,7 @@ ArenaPurgeResult arena_t::Purge(PurgeCondition aCond, PurgeStats& aStats) {
 
     if (!ShouldContinuePurge(aCond)) {
       mIsPurgePending = false;
-      return ReachedThreshold;
+      return ReachedThresholdOrBusy;
     }
 
     // Take a single chunk and attempt to purge some of its dirty pages.  The
@@ -1920,16 +1920,17 @@ ArenaPurgeResult arena_t::Purge(PurgeCondition aCond, PurgeStats& aStats) {
       chunk = mChunksDirty.Last();
     }
     if (!chunk) {
-      // There are chunks with dirty pages (because mNumDirty > 0 above) but
-      // they're not in mChunksDirty.  That can happen if they're busy being
-      // purged by other threads.
       // We have to clear the flag to preserve the invariant that if Purge()
       // returns anything other than NotDone then the flag is clear. If there's
       // more purging work to do in other chunks then either other calls to
       // Purge() (in other threads) will handle it or we rely on
       // ShouldStartPurge() returning true at some point in the future.
       mIsPurgePending = false;
-      return Busy;
+
+      // There are chunks with dirty pages (because mNumDirty > 0 above) but
+      // they're not in mChunksDirty, they might not have enough dirty pages.
+      // Or maybe they're busy being purged by other threads.
+      return ReachedThresholdOrBusy;
     }
     MOZ_ASSERT(chunk->mNumDirty > 0);
 
@@ -1984,7 +1985,7 @@ ArenaPurgeResult arena_t::Purge(PurgeCondition aCond, PurgeStats& aStats) {
       }
       // There's nothing else to do here, our caller may execute Purge() again
       // if continue_purge_arena is true.
-      return continue_purge_arena ? NotDone : ReachedThreshold;
+      return continue_purge_arena ? NotDone : ReachedThresholdOrBusy;
     }
 
 #ifdef MALLOC_DECOMMIT
@@ -2033,7 +2034,7 @@ ArenaPurgeResult arena_t::Purge(PurgeCondition aCond, PurgeStats& aStats) {
     purged_once = true;
   }
 
-  return continue_purge_arena ? NotDone : ReachedThreshold;
+  return continue_purge_arena ? NotDone : ReachedThresholdOrBusy;
 }
 
 ArenaPurgeResult arena_t::PurgeLoop(PurgeCondition aCond, const char* aCaller,
diff --git a/memory/build/mozjemalloc_types.h b/memory/build/mozjemalloc_types.h
@@ -222,15 +222,14 @@ static inline bool jemalloc_ptr_is_freed_page(jemalloc_ptr_info_t* info) {
 
 // The result of purging memory from a sigle arena
 enum ArenaPurgeResult {
-  // The stop threshold of dirty pages was reached.
-  ReachedThreshold,
+  // The stop threshold of dirty pages was reached or all the remaining chunks
+  // that may have dirty pages are busy.  The allocator can't always tell the
+  // difference between these conditions.
+  ReachedThresholdOrBusy,
 
   // There's more chunks in this arena that could be purged.
   NotDone,
 
-  // The only chunks with dirty pages are busy being purged by other threads.
-  Busy,
-
   // The arena needs to be destroyed by the caller.
   Dying,
 };
diff --git a/tools/profiler/core/memory_markers.cpp b/tools/profiler/core/memory_markers.cpp
@@ -68,15 +68,12 @@ class GeckoProfilerMallocCallbacks : public MallocProfilerCallbacks {
                        ArenaPurgeResult aResult) override {
     const char* result = nullptr;
     switch (aResult) {
-      case ReachedThreshold:
-        result = "Reached dirty page threshold";
+      case ReachedThresholdOrBusy:
+        result = "Can't find enough dirty memory to purge";
         break;
       case NotDone:
         result = "Purge exited early (eg caller set a time budget)";
         break;
-      case Busy:
-        result = "Last chunk is busy being purged on another thread";
-        break;
       case Dying:
         result = "Arena is being destroyed";
         break;