Release memory to OS only when the requested range covers the entire page

Summary:
The current code was sometimes attempting to release huge chunks of
memory due to undesired RoundUp/RoundDown interaction when the requested
range is fully contained within one memory page.

Reviewers: eugenis

Subscribers: kubabrecka, llvm-commits

Patch by Aleksey Shlyapnikov.

Differential Revision: https://reviews.llvm.org/D27228

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@288271 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 8 deletions

diff --git a/lib/sanitizer_common/sanitizer_allocator_primary64.h b/lib/sanitizer_common/sanitizer_allocator_primary64.h
index 4beb109ca..f2d94a07a 100644
--- a/lib/sanitizer_common/sanitizer_allocator_primary64.h
+++ b/lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -458,17 +458,11 @@ class SizeClassAllocator64 {
     }
   }
 
-  bool MaybeReleaseChunkRange(uptr region_beg, uptr chunk_size,
+  void MaybeReleaseChunkRange(uptr region_beg, uptr chunk_size,
                               CompactPtrT first, CompactPtrT last) {
     uptr beg_ptr = CompactPtrToPointer(region_beg, first);
     uptr end_ptr = CompactPtrToPointer(region_beg, last) + chunk_size;
-    const uptr page_size = GetPageSizeCached();
-    CHECK_GE(end_ptr - beg_ptr, page_size);
-    beg_ptr = RoundUpTo(beg_ptr, page_size);
-    end_ptr = RoundDownTo(end_ptr, page_size);
-    if (end_ptr == beg_ptr) return false;
-    ReleaseMemoryToOS(beg_ptr, end_ptr - beg_ptr);
-    return true;
+    ReleaseMemoryPagesToOS(beg_ptr, end_ptr);
   }
 
   // Attempts to release some RAM back to OS. The region is expected to be