From 616c922eb870c5365f1957b970d7042600f76787 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20Inf=C3=BChr?= <dinfuehr@chromium.org>
Date: Thu, 29 Sep 2022 15:27:03 +0200
Subject: [PATCH] [heap] Support code space sweeping on background threads
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Since code space is now swept concurrently as well, background threads
can now sweep code pages on allocation failures as well.

Change-Id: I493eb9bd8b1a95f58ddb96a5ced7f87d9397da47
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3929038
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83489}
---
 src/heap/paged-spaces.cc | 51 ++++++++++++++++------------------------
 src/heap/paged-spaces.h  |  4 ----
 2 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/src/heap/paged-spaces.cc b/src/heap/paged-spaces.cc
index a6ea1cc941..6b4d143136 100644
--- a/src/heap/paged-spaces.cc
+++ b/src/heap/paged-spaces.cc
@@ -684,26 +684,23 @@ PagedSpaceBase::RawAllocateBackground(LocalHeap* local_heap,
                                                  max_size_in_bytes, origin);
     if (result) return result;
 
-    if (IsSweepingAllowedOnThread(local_heap)) {
-      // Now contribute to sweeping from background thread and then try to
-      // reallocate.
-      int max_freed;
-      {
-        TRACE_GC_EPOCH(heap()->tracer(),
-                       GCTracer::Scope::MC_BACKGROUND_SWEEPING,
-                       ThreadKind::kBackground);
-        const int kMaxPagesToSweep = 1;
-        max_freed = collector->sweeper()->ParallelSweepSpace(
-            identity(), Sweeper::SweepingMode::kLazyOrConcurrent,
-            static_cast<int>(min_size_in_bytes), kMaxPagesToSweep);
-        RefillFreeList(collector->sweeper());
-      }
+    // Now contribute to sweeping from background thread and then try to
+    // reallocate.
+    int max_freed;
+    {
+      TRACE_GC_EPOCH(heap()->tracer(), GCTracer::Scope::MC_BACKGROUND_SWEEPING,
+                     ThreadKind::kBackground);
+      const int kMaxPagesToSweep = 1;
+      max_freed = collector->sweeper()->ParallelSweepSpace(
+          identity(), Sweeper::SweepingMode::kLazyOrConcurrent,
+          static_cast<int>(min_size_in_bytes), kMaxPagesToSweep);
+      RefillFreeList(collector->sweeper());
+    }
 
-      if (static_cast<size_t>(max_freed) >= min_size_in_bytes) {
-        result = TryAllocationFromFreeListBackground(min_size_in_bytes,
-                                                     max_size_in_bytes, origin);
-        if (result) return result;
-      }
+    if (static_cast<size_t>(max_freed) >= min_size_in_bytes) {
+      result = TryAllocationFromFreeListBackground(min_size_in_bytes,
+                                                   max_size_in_bytes, origin);
+      if (result) return result;
     }
   }
 
@@ -715,13 +712,11 @@ PagedSpaceBase::RawAllocateBackground(LocalHeap* local_heap,
 
   if (collector->sweeping_in_progress()) {
     // Complete sweeping for this space.
-    if (IsSweepingAllowedOnThread(local_heap)) {
-      TRACE_GC_EPOCH(heap()->tracer(), GCTracer::Scope::MC_BACKGROUND_SWEEPING,
-                     ThreadKind::kBackground);
-      collector->DrainSweepingWorklistForSpace(identity());
+    TRACE_GC_EPOCH(heap()->tracer(), GCTracer::Scope::MC_BACKGROUND_SWEEPING,
+                   ThreadKind::kBackground);
+    collector->DrainSweepingWorklistForSpace(identity());
 
-      RefillFreeList(collector->sweeper());
-    }
+    RefillFreeList(collector->sweeper());
 
     // Last try to acquire memory from free list.
     return TryAllocationFromFreeListBackground(min_size_in_bytes,
@@ -777,12 +772,6 @@ PagedSpaceBase::TryAllocationFromFreeListBackground(size_t min_size_in_bytes,
   return std::make_pair(start, used_size_in_bytes);
 }
 
-bool PagedSpaceBase::IsSweepingAllowedOnThread(LocalHeap* local_heap) const {
-  // Code space sweeping is only allowed on main thread.
-  return (local_heap && local_heap->is_main_thread()) ||
-         identity() != CODE_SPACE;
-}
-
 #ifdef DEBUG
 void PagedSpaceBase::Print() {}
 #endif
diff --git a/src/heap/paged-spaces.h b/src/heap/paged-spaces.h
index bfb8d44451..fd30ce2d92 100644
--- a/src/heap/paged-spaces.h
+++ b/src/heap/paged-spaces.h
@@ -353,10 +353,6 @@ class V8_EXPORT_PRIVATE PagedSpaceBase
 
   bool HasPages() const { return first_page() != nullptr; }
 
-  // Returns whether sweeping of this space is safe on this thread. Code space
-  // sweeping is only allowed on the main thread.
-  bool IsSweepingAllowedOnThread(LocalHeap* local_heap) const;
-
   // Cleans up the space, frees all pages in this space except those belonging
   // to the initial chunk, uncommits addresses in the initial chunk.
   void TearDown();