[compiler-rt] 6ddb25e - [scudo] increase frames per stack to 16 for stack depot (#82427)

[via llvm-commits]

Author: Florian Mayer
Date: 2024-02-22T11:19:02-08:00
New Revision: 6ddb25ed9ca2cb0f4ad8f402d7411ac3328f598d

URL: https://github.com/llvm/llvm-project/commit/6ddb25ed9ca2cb0f4ad8f402d7411ac3328f598d
DIFF: https://github.com/llvm/llvm-project/commit/6ddb25ed9ca2cb0f4ad8f402d7411ac3328f598d.diff

LOG: [scudo] increase frames per stack to 16 for stack depot (#82427)

8 was very low and it is likely that in real workloads we have more than
an average of 8 frames per stack given on Android we have 3 at the
bottom: __start_main, __libc_init, main, and three at the top: malloc,
scudo_malloc and Allocator::allocate. That leaves 2 frames for
application code, which is clearly unreasonable.

Added: 
    

Modified: 
    compiler-rt/lib/scudo/standalone/combined.h

Removed: 
    


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diff  --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index f3c3d757c9f128..f13cf9498a7932 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -1522,7 +1522,12 @@ class Allocator {
     constexpr u32 kStacksPerRingBufferEntry = 2;
     constexpr u32 kMaxU32Pow2 = ~(UINT32_MAX >> 1);
     static_assert(isPowerOfTwo(kMaxU32Pow2));
-    constexpr u32 kFramesPerStack = 8;
+    // On Android we always have 3 frames at the bottom: __start_main,
+    // __libc_init, main, and 3 at the top: malloc, scudo_malloc and
+    // Allocator::allocate. This leaves 10 frames for the user app. The next
+    // smallest power of two (8) would only leave 2, which is clearly too
+    // little.
+    constexpr u32 kFramesPerStack = 16;
     static_assert(isPowerOfTwo(kFramesPerStack));
 
     // We need StackDepot to be aligned to 8-bytes so the ring we store after