[compiler-rt] 3a713ae - [SanitizerCommon] Reduce wasting memory in LowLevelAllocator.

[Igor Kudrin via llvm-commits]

Author: Igor Kudrin
Date: 2019-12-11T12:44:55+07:00
New Revision: 3a713ae5fa64a0b2043bd6748b87d4ba7f7c2fce

URL: https://github.com/llvm/llvm-project/commit/3a713ae5fa64a0b2043bd6748b87d4ba7f7c2fce
DIFF: https://github.com/llvm/llvm-project/commit/3a713ae5fa64a0b2043bd6748b87d4ba7f7c2fce.diff

LOG: [SanitizerCommon] Reduce wasting memory in LowLevelAllocator.

MmapOrDie allocates memory multiple to page size. LowLevelAllocator
should use all that memory for the internal buffer because there are
chances that subsequent requests may be small enough to fit in that
space.

Differential Revision: https://reviews.llvm.org/D71275

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
    compiler-rt/lib/sanitizer_common/tests/sanitizer_allocator_test.cpp

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
index 8d07906cca03..906d4af7f5ee 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
@@ -213,7 +213,7 @@ void *LowLevelAllocator::Allocate(uptr size) {
   // Align allocation size.
   size = RoundUpTo(size, low_level_alloc_min_alignment);
   if (allocated_end_ - allocated_current_ < (sptr)size) {
-    uptr size_to_allocate = Max(size, GetPageSizeCached());
+    uptr size_to_allocate = RoundUpTo(size, GetPageSizeCached());
     allocated_current_ =
         (char*)MmapOrDie(size_to_allocate, __func__);
     allocated_end_ = allocated_current_ + size_to_allocate;

diff  --git a/compiler-rt/lib/sanitizer_common/tests/sanitizer_allocator_test.cpp b/compiler-rt/lib/sanitizer_common/tests/sanitizer_allocator_test.cpp
index 782011b2503b..ff1f7f9f5d2b 100644
--- a/compiler-rt/lib/sanitizer_common/tests/sanitizer_allocator_test.cpp
+++ b/compiler-rt/lib/sanitizer_common/tests/sanitizer_allocator_test.cpp
@@ -1404,4 +1404,15 @@ TEST(SanitizerCommon, ThreadedTwoLevelByteMap) {
   EXPECT_EQ((uptr)TestMapUnmapCallback::unmap_count, m.size1());
 }
 
+TEST(SanitizerCommon, LowLevelAllocatorShouldRoundUpSizeOnAlloc) {
+  // When allocating a memory block slightly bigger than a memory page and
+  // LowLevelAllocator calls MmapOrDie for the internal buffer, it should round
+  // the size up to the page size, so that subsequent calls to the allocator
+  // can use the remaining space in the last allocated page.
+  static LowLevelAllocator allocator;
+  char *ptr1 = (char *)allocator.Allocate(GetPageSizeCached() + 16);
+  char *ptr2 = (char *)allocator.Allocate(16);
+  EXPECT_EQ(ptr2, ptr1 + GetPageSizeCached() + 16);
+}
+
 #endif  // #if !SANITIZER_DEBUG