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From 0128c5a9eeee0d3fc0deb9129dd20eb79338c8f4 Mon Sep 17 00:00:00 2001
From: Koen Kooi <koen.kooi@linaro.org>
Date: Mon, 2 Mar 2015 19:08:59 +0800
Subject: [PATCH 4/5] mozbug746112-no-decommit-on-large-pages
---
Upstream-status: Pending
js/src/gc/Heap.h | 15 ++++++++++-----
js/src/jsgc.cpp | 15 ++++++++++++---
2 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/js/src/gc/Heap.h b/js/src/gc/Heap.h
index b8f8c78..1cfd269 100644
--- a/js/src/gc/Heap.h
+++ b/js/src/gc/Heap.h
@@ -103,26 +103,31 @@ struct Cell
};
/*
- * Page size is 4096 by default, except for SPARC, where it is 8192.
+ * Page size must be static to support our arena pointer optimizations, so we
+ * are forced to support each platform with non-4096 pages as a special case.
+ * Note: The freelist supports a maximum arena shift of 15.
* Note: Do not use JS_CPU_SPARC here, this header is used outside JS.
* Bug 692267: Move page size definition to gc/Memory.h and include it
* directly once jsgc.h is no longer an installed header.
*/
#if defined(SOLARIS) && (defined(__sparc) || defined(__sparcv9))
const size_t PageShift = 13;
+const size_t ArenaShift = PageShift;
+#elif defined(__powerpc__)
+const size_t PageShift = 16;
+const size_t ArenaShift = 12;
#else
const size_t PageShift = 12;
+const size_t ArenaShift = PageShift;
#endif
const size_t PageSize = size_t(1) << PageShift;
+const size_t ArenaSize = size_t(1) << ArenaShift;
+const size_t ArenaMask = ArenaSize - 1;
const size_t ChunkShift = 20;
const size_t ChunkSize = size_t(1) << ChunkShift;
const size_t ChunkMask = ChunkSize - 1;
-const size_t ArenaShift = PageShift;
-const size_t ArenaSize = PageSize;
-const size_t ArenaMask = ArenaSize - 1;
-
/*
* This is the maximum number of arenas we allow in the FreeCommitted state
* before we trigger a GC_SHRINK to release free arenas to the OS.
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index b3caf05..a258d2d 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -251,6 +251,13 @@ static const int BackgroundPhaseLength[] = {
sizeof(BackgroundPhaseStrings) / sizeof(AllocKind)
};
+/* Unused memory decommiting requires the arena size match the page size. */
+static bool
+DecommitEnabled()
+{
+ return PageSize == ArenaSize;
+}
+
#ifdef DEBUG
void
ArenaHeader::checkSynchronizedWithFreeList() const
@@ -742,7 +749,8 @@ Chunk::fetchNextDecommittedArena()
decommittedArenas.unset(offset);
Arena *arena = &arenas[offset];
- MarkPagesInUse(arena, ArenaSize);
+ if (DecommitEnabled())
+ MarkPagesInUse(arena, ArenaSize);
arena->aheader.setAsNotAllocated();
return &arena->aheader;
@@ -2731,7 +2739,7 @@ DecommitArenasFromAvailableList(JSRuntime *rt, Chunk **availableListHeadp)
chunk->removeFromAvailableList();
size_t arenaIndex = Chunk::arenaIndex(aheader->arenaAddress());
- bool ok;
+ bool ok = true;
{
/*
* If the main thread waits for the decommit to finish, skip
@@ -2741,7 +2749,8 @@ DecommitArenasFromAvailableList(JSRuntime *rt, Chunk **availableListHeadp)
Maybe<AutoUnlockGC> maybeUnlock;
if (!rt->isHeapBusy())
maybeUnlock.construct(rt);
- ok = MarkPagesUnused(aheader->getArena(), ArenaSize);
+ if (DecommitEnabled())
+ ok = MarkPagesUnused(aheader->getArena(), ArenaSize);
}
if (ok) {
--
1.9.3
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