[compiler-rt] [scudo] Improve the message of region exhausted (PR #68444)

[via llvm-commits]

https://github.com/ChiaHungDuan created https://github.com/llvm/llvm-project/pull/68444

In this CL, we move the printing of allocator stats from primary.h to combined.h. This will also dump the secondary stats and reduce the log spam when an OOM happens

Also change the symbol `F` to `E` to indicate region pages exhausted. It means the region can't map more pages for blocks but it may still have free blocks to allocate. `F` may hint the failure of fatel error in the region. Also update the related comments.

>From 727599a1c367af76a8cd9ce7d72dab34dc5b9315 Mon Sep 17 00:00:00 2001
From: Chia-hung Duan <chiahungduan at google.com>
Date: Fri, 6 Oct 2023 20:12:20 +0000
Subject: [PATCH] [scudo] Improve the message of region exhausted

In this CL, we move the printing of allocator stats from primary.h to
combined.h. This will also dump the secondary stats and reduce the log
spam when an OOM happens

Also change the symbol `F` to `E` to indicate region pages exhausted.
It means the region can't map more pages for blocks but it may still
have free blocks to allocate. `F` may hint the failure of fatel error in
the region. Also update the related comments.
---
 compiler-rt/lib/scudo/standalone/combined.h  |  8 ++++----
 compiler-rt/lib/scudo/standalone/primary64.h | 18 ++++++------------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index b013f03a73ae40d..b1700e5ecef7f5b 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -367,10 +367,9 @@ class Allocator {
       auto *TSD = TSDRegistry.getTSDAndLock(&UnlockRequired);
       TSD->assertLocked(/*BypassCheck=*/!UnlockRequired);
       Block = TSD->getCache().allocate(ClassId);
-      // If the allocation failed, the most likely reason with a 32-bit primary
-      // is the region being full. In that event, retry in each successively
-      // larger class until it fits. If it fails to fit in the largest class,
-      // fallback to the Secondary.
+      // If the allocation failed, retry in each successively larger class until
+      // it fits. If it fails to fit in the largest class, fallback to the
+      // Secondary.
       if (UNLIKELY(!Block)) {
         while (ClassId < SizeClassMap::LargestClassId && !Block)
           Block = TSD->getCache().allocate(++ClassId);
@@ -388,6 +387,7 @@ class Allocator {
     if (UNLIKELY(!Block)) {
       if (Options.get(OptionBit::MayReturnNull))
         return nullptr;
+      printStats();
       reportOutOfMemory(NeededSize);
     }
 
diff --git a/compiler-rt/lib/scudo/standalone/primary64.h b/compiler-rt/lib/scudo/standalone/primary64.h
index ed0c4deaac2c8bf..6d160b4c64d75fc 100644
--- a/compiler-rt/lib/scudo/standalone/primary64.h
+++ b/compiler-rt/lib/scudo/standalone/primary64.h
@@ -214,7 +214,7 @@ template <typename Config> class SizeClassAllocator64 {
         return B;
     }
 
-    bool PrintStats = false;
+    bool ReportRegionExhausted = false;
     TransferBatch *B = nullptr;
 
     while (true) {
@@ -235,19 +235,13 @@ template <typename Config> class SizeClassAllocator64 {
       const bool RegionIsExhausted = Region->Exhausted;
       if (!RegionIsExhausted)
         B = populateFreeListAndPopBatch(C, ClassId, Region);
-      PrintStats = !RegionIsExhausted && Region->Exhausted;
+      ReportRegionExhausted = !RegionIsExhausted && Region->Exhausted;
       break;
     }
 
-    // Note that `getStats()` requires locking each region so we can't call it
-    // while locking the Region->Mutex in the above.
-    if (UNLIKELY(PrintStats)) {
-      ScopedString Str;
-      getStats(&Str);
-      Str.append(
-          "Scudo OOM: The process has exhausted %zuM for size class %zu.\n",
-          RegionSize >> 20, getSizeByClassId(ClassId));
-      Str.output();
+    if (UNLIKELY(ReportRegionExhausted)) {
+      Printf("Can't populate more pages for size class %zu.\n",
+             getSizeByClassId(ClassId));
 
       // Theoretically, BatchClass shouldn't be used up. Abort immediately  when
       // it happens.
@@ -978,7 +972,7 @@ template <typename Config> class SizeClassAllocator64 {
         "%s %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
         "inuse: %6zu total: %6zu releases: %6zu last "
         "released: %6zuK latest pushed bytes: %6zuK region: 0x%zx (0x%zx)\n",
-        Region->Exhausted ? "F" : " ", ClassId, getSizeByClassId(ClassId),
+        Region->Exhausted ? "E" : " ", ClassId, getSizeByClassId(ClassId),
         Region->MemMapInfo.MappedUser >> 10, Region->FreeListInfo.PoppedBlocks,
         Region->FreeListInfo.PushedBlocks, InUseBlocks, TotalChunks,
         Region->ReleaseInfo.RangesReleased,