[memprof] Replace the block cache with a hashmap.

[snehasish]

Summary

The existing implementation uses a cache + eviction based scheme to
record heap profile information. This design was adopted to ensure a
constant memory overhead (due to fixed number of cache entries) along
with incremental write-to-disk for evictions. We find that since the
number to entries to track is O(unique-allocation-contexts) the overhead
of keeping all contexts in memory is not very high. On a clang workload,
the max number of unique allocation contexts was ~35K, median ~11K.
For each context, we (currently) store 64 bytes of data - this amounts
to 5.5MB (max). Given the low overheads for a complex workload, we can
simplify the implementation by using a hashmap without eviction.

Also refactored out the MemInfoBlock struct into a separate file so that
it we can refer to it from a different module. Longer term, this
will be replaced by a .inc file shared between compiler-rt and
llvm/ProfileData.

[snehasish]

Cleanup some rebase issues.

[vitalybuka]

compiler-rt/lib/memprof/memprof_allocator.cpp

193

previosly we had lock here

258–264

You can fix race between print merge by unlocking allocator later

however it does not solves merge vs merge race

compiler-rt/lib/memprof/memprof_mibmap.h

6

AddrHashMap is useful if we need to delete items or address is full 64bit address space
D111608 just today made alloc_context_id is very sequential [0..2^31), so you can use simple structure:

`
using MIBMapTy = TwoLevelMap<MemInfoBlock, StackDepot::kNodesSize1, StackDepot::kNodesSize2>

inline void InsertOrMerge(const uptr Id, const MemInfoBlock &Block,
                          MIBMapTy &Map) {
  Map[id].Merge();
}

Print(const MIBMapTy &Map) {
  for (u32 i = 0; Map.contains(i) ; ++i)
       Map[i].Print(); 
}

After that you have same without ForEach implementation
Still Merge vs Merge is not solved

20

Handle does not lock content of MemInfoBlock, so it's a data race on Merge

[snehasish]

Address merge data race.

[snehasish]

Address comments.

compiler-rt/lib/memprof/memprof_allocator.cpp

258–264

Good idea. Thanks!

compiler-rt/lib/memprof/memprof_mibmap.h

6

I'm very hesitant to rely on the sequential ordering of allocation context ids. I think it would be best for memprof to treat it as an opaque value so that the underlying implementation can evolve. For example, even memprof may store additional data which may not be indexed by a calling context.

So I would prefer it if we continue with the ForEach implementation in the parent patch unless you have a strong opinion.

20

Added locking in InsertOrMerge based on the context id. PTAL.

[snehasish]

compiler-rt/lib/memprof/memprof_allocator.cpp

258–264

Actually I think this does not solve the Merge-Print race. The InsertOrMerge call in the Deallocate hook (L633 in the original source) is not protected by a lock. We could add more synchronization to ensure that we only start "destructing" after all other threads have finished running Deallocate but I don't think that's necessary. It's ok to be a little lossy in this case. @tejohnson Wdyt?

[vitalybuka]

compiler-rt/lib/memprof/memprof_mibmap.cpp

25

With such hashing Idx->2^8 very likely different cores will compete for the same mutex making this as bad as a single global mutex.

Size of MemInfoBlock is quite large,
Spin mutex is just 1 byte? why not put mutex inside of each MemInfoBlock?

and then you can lock same mutex in Print solving all issues above.

compiler-rt/lib/memprof/memprof_mibmap.h

6

I would recommend you to keep it simple, which is TwoLevelMap.
It requires trivial change to this patch, and you always can recover ForEach if needed. Very likely evolution of memprof will lead you to unexpected places where neither solution is good enough.

[snehasish]

With such hashing Idx->2^8 very likely different cores will compete for the same mutex making this as bad as a single global mutex.

Yes, the contention here (on 8 locks) is more than what was present in the prior implementation which used a lock per cache set (default number of sets ~16K). However, I ran this implementation and compared the overheads on a large internal workload and found them to roughly be the same order of magnitude, i.e. both implementations (hashmap and prior cache-based) are 2X-3X faster than PGO.

Size of MemInfoBlock is quite large,
Spin mutex is just 1 byte? why not put mutex inside of each MemInfoBlock?
and then you can lock same mutex in Print solving all issues above.

That's a neat idea. For context: we intend to share the MemInfoBlock entry definition across compiler-rt and llvm/ProfileData using a .inc style header (details in RFC 1]). I will evaluate the performance benefit of this added 1-byte to see whether it makes sense, thanks for the suggestion!

I would recommend you to keep it simple, which is TwoLevelMap.
It requires trivial change to this patch, and you always can recover ForEach if needed. Very likely evolution of memprof will lead you to unexpected places where neither solution is good enough.

I agree that the evolution of memprof will likely outgrow the current choice. I am still in favour of the AddrHashMap extension since it allows us to be not rely on the sequential context id. I will defer to Teresa for making the decision.

[1] https://lists.llvm.org/pipermail/llvm-dev/2021-September/153007.html

[tejohnson]

In D111676#3065917, @snehasish wrote:

I would recommend you to keep it simple, which is TwoLevelMap.
It requires trivial change to this patch, and you always can recover ForEach if needed. Very likely evolution of memprof will lead you to unexpected places where neither solution is good enough.

I agree that the evolution of memprof will likely outgrow the current choice. I am still in favour of the AddrHashMap extension since it allows us to be not rely on the sequential context id. I will defer to Teresa for making the decision.

I'm also hesitant to rely on having sequential ids in this code.

compiler-rt/lib/memprof/memprof_allocator.cpp

258–264

Yes, I think we can accept some loss in case of a race here. It isn't a new issue with this patch in any case. If necessary we can add more synchronization later.

compiler-rt/lib/memprof/memprof_mibmap.h

11

I'm skeptical that 199 is large enough to avoid too much performance overhead from collisions and the resulting traversal. Why so much smaller than the default MIB Cache size?

[vitalybuka]

compiler-rt/lib/memprof/memprof_allocator.cpp

258–264

having 1 byte mutex in Memblock solves both Print/Merge and Merge/Merge issues

[snehasish]

Address comments.

• Tune the address map size based on internal workload and double checked on clang.
• Guard deallocation insertions to ensure map has been initialized.
• Use a pointer as value in the map instead of MIB.
• Store a 1 byte mutex for each MIB to allow fine-grained locking.

[snehasish]

Remove accidental change to llvm/cmake/modules/HandleLLVMOptions.cmake

[snehasish]

PTAL, thanks!

compiler-rt/lib/memprof/memprof_mibmap.h

6

After internal discussion and evaluation on a large workload we decided to keep using the AddrHashMap implementation for now since it gives us more flexibility.

[tejohnson]

LGTM but looking through the tests I added it looks like I was remiss in adding one that will result in a merge - could you add one with this change?

[vitalybuka]

compiler-rt/lib/memprof/memprof_meminfoblock.h

11 ↗

(On Diff #384816)

Can you extract a patch which moves MemInfoBlock into memprof_meminfoblock.h as much as possible unchanged?

[snehasish]

Update diff after splitting out MemInfoBlock changes as a separate patch.

[vitalybuka]

compiler-rt/lib/memprof/CMakeLists.txt

39

this belongs to another patch

[snehasish]

Update CMakelist and add merge test.

[snehasish]

Thanks for the review Vitaly. I've cleaned up the CMakelist and added a test for to check merging of mibs. @tejohnson PTAL, thanks!

[tejohnson]

lgtm

[snehasish]

Rebase.

compiler-rt/lib/memprof/CMakeLists.txt

 # Build for the Memory Profiler runtime support library.
 
 set(MEMPROF_SOURCES
   memprof_allocator.cpp
   memprof_descriptions.cpp
   memprof_flags.cpp
   memprof_interceptors.cpp
   memprof_interceptors_memintrinsics.cpp
   memprof_linux.cpp
   memprof_malloc_linux.cpp
+  memprof_mibmap.cpp
   memprof_posix.cpp
   memprof_rtl.cpp
   memprof_shadow_setup.cpp
   memprof_stack.cpp
   memprof_stats.cpp
   memprof_thread.cpp
   )
 
SET(MEMPROF_HEADERS
   memprof_flags.h
   memprof_flags.inc
   memprof_init_version.h
   memprof_interceptors.h
   memprof_interceptors_memintrinsics.h
   memprof_interface_internal.h
   memprof_internal.h
   memprof_mapping.h
   memprof_meminfoblock.h
+  memprof_mibmap.h
   memprof_stack.h
   memprof_stats.h
   memprof_thread.h
   )
 
 include_directories(..)
 
 set(MEMPROF_CFLAGS ${SANITIZER_COMMON_CFLAGS})

compiler-rt/lib/memprof/memprof_allocator.cpp

 // Implementation of MemProf's memory allocator, which uses the allocator
 // from sanitizer_common.
 //
 //===----------------------------------------------------------------------===//
 
 #include "memprof_allocator.h"
 #include "memprof_mapping.h"
 #include "memprof_meminfoblock.h"
+#include "memprof_mibmap.h"
 #include "memprof_stack.h"
 #include "memprof_thread.h"
 #include "sanitizer_common/sanitizer_allocator_checks.h"
 #include "sanitizer_common/sanitizer_allocator_interface.h"
 #include "sanitizer_common/sanitizer_allocator_report.h"
 #include "sanitizer_common/sanitizer_errno.h"
 #include "sanitizer_common/sanitizer_file.h"
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_internal_defs.h"
 #include "sanitizer_common/sanitizer_list.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 
 #include <sched.h>
-#include <stdlib.h>
 #include <time.h>
 
 namespace __memprof {
 
 static int GetCpuId(void) {
   // _memprof_preinit is called via the preinit_array, which subsequently calls
   // malloc. Since this is before _dl_init calls VDSO_SETUP, sched_getcpu
   // will seg fault as the address of __vdso_getcpu will be null.
void MemprofMapUnmapCallback::OnUnmap(uptr p, uptr size) const {
   thread_stats.munmaped += size;
 }
 
 AllocatorCache *GetAllocatorCache(MemprofThreadLocalMallocStorage *ms) {
   CHECK(ms);
   return &ms->allocator_cache;
 }
 
-struct SetEntry {
-  SetEntry() : id(0), MIB() {}
-  bool Empty() { return id == 0; }
-  void Print() {
-    CHECK(!Empty());
-    MIB.Print(id, flags()->print_terse);
-  }
-  // The stack id
-  u64 id;
-  MemInfoBlock MIB;
-};
-
-struct CacheSet {
-  enum { kSetSize = 4 };
-
-  void PrintAll() {
-    for (int i = 0; i < kSetSize; i++) {
-      if (Entries[i].Empty())
-        continue;
-      Entries[i].Print();
-    }
-  }
-  void insertOrMerge(u64 new_id, MemInfoBlock &newMIB) {
-    SpinMutexLock l(&SetMutex);
-    AccessCount++;
-
-    for (int i = 0; i < kSetSize; i++) {
-      auto id = Entries[i].id;
-      // Check if this is a hit or an empty entry. Since we always move any
-      // filled locations to the front of the array (see below), we don't need
-      // to look after finding the first empty entry.
-      if (id == new_id || !id) {
-        if (id == 0) {
-          Entries[i].id = new_id;
-          Entries[i].MIB = newMIB;
-        } else {
-          Entries[i].MIB.Merge(newMIB);
-        }
-        // Assuming some id locality, we try to swap the matching entry
-        // into the first set position.
-        if (i != 0) {
-          auto tmp = Entries[0];
-          Entries[0] = Entries[i];
-          Entries[i] = tmp;
-        }
-        return;
-      }
-    }
-
-    // Miss
-    MissCount++;
-
-    // We try to find the entries with the lowest alloc count to be evicted:
-    int min_idx = 0;
-    u64 min_count = Entries[0].MIB.alloc_count;
-    for (int i = 1; i < kSetSize; i++) {
-      CHECK(!Entries[i].Empty());
-      if (Entries[i].MIB.alloc_count < min_count) {
-        min_idx = i;
-        min_count = Entries[i].MIB.alloc_count;
-      }
-    }
-
-    // Print the evicted entry profile information
-    if (!flags()->print_terse)
-      Printf("Evicted:\n");
-    Entries[min_idx].Print();
-
-    // Similar to the hit case, put new MIB in first set position.
-    if (min_idx != 0)
-      Entries[min_idx] = Entries[0];
-    Entries[0].id = new_id;
-    Entries[0].MIB = newMIB;
-  }
-
-  void PrintMissRate(int i) {
-    u64 p = AccessCount ? MissCount * 10000ULL / AccessCount : 0;
-    Printf("Set %d miss rate: %d / %d = %5llu.%02llu%%\n", i, MissCount,
-           AccessCount, p / 100, p % 100);
-  }
-
-  SetEntry Entries[kSetSize];
-  u32 AccessCount = 0;
-  u32 MissCount = 0;
-  SpinMutex SetMutex;
-};
-
-struct MemInfoBlockCache {
-  MemInfoBlockCache() {
-    if (common_flags()->print_module_map)
-      DumpProcessMap();
-    if (flags()->print_terse)
-      MemInfoBlock::printHeader();
-    Sets =
-        (CacheSet *)malloc(sizeof(CacheSet) * flags()->mem_info_cache_entries);
-    Constructed = true;
-  }
-
-  ~MemInfoBlockCache() { free(Sets); }
-
-  void insertOrMerge(u64 new_id, MemInfoBlock &newMIB) {
-    u64 hv = new_id;
-
-    // Use mod method where number of entries should be a prime close to power
-    // of 2.
-    hv %= flags()->mem_info_cache_entries;
-
-    return Sets[hv].insertOrMerge(new_id, newMIB);
-  }
-
-  void PrintAll() {
-    for (int i = 0; i < flags()->mem_info_cache_entries; i++) {
-      Sets[i].PrintAll();
-    }
-  }
-
-  void PrintMissRate() {
-    if (!flags()->print_mem_info_cache_miss_rate)
-      return;
-    u64 MissCountSum = 0;
-    u64 AccessCountSum = 0;
-    for (int i = 0; i < flags()->mem_info_cache_entries; i++) {
-      MissCountSum += Sets[i].MissCount;
-      AccessCountSum += Sets[i].AccessCount;
-    }
-    u64 p = AccessCountSum ? MissCountSum * 10000ULL / AccessCountSum : 0;
-    Printf("Overall miss rate: %llu / %llu = %5llu.%02llu%%\n", MissCountSum,
-           AccessCountSum, p / 100, p % 100);
-    if (flags()->print_mem_info_cache_miss_rate_details)
-      for (int i = 0; i < flags()->mem_info_cache_entries; i++)
-        Sets[i].PrintMissRate(i);
-  }
-
-  CacheSet *Sets;
-  // Flag when the Sets have been allocated, in case a deallocation is called
-  // very early before the static init of the Allocator and therefore this table
-  // have completed.
-  bool Constructed = false;
-};
-
 // Accumulates the access count from the shadow for the given pointer and size.
 u64 GetShadowCount(uptr p, u32 size) {
   u64 *shadow = (u64 *)MEM_TO_SHADOW(p);
   u64 *shadow_end = (u64 *)MEM_TO_SHADOW(p + size);
   u64 count = 0;
   for (; shadow <= shadow_end; shadow++)
     count += *shadow;
   return count;
struct Allocator {
 
   MemprofAllocator allocator;
   StaticSpinMutex fallback_mutex;
   AllocatorCache fallback_allocator_cache;
 
   uptr max_user_defined_malloc_size;
   atomic_uint8_t rss_limit_exceeded;
 
-  MemInfoBlockCache MemInfoBlockTable;
+  // Holds the mapping of stack ids to MemInfoBlocks.
+  MIBMapTy MIBMap;
+
   bool destructing;
+  bool constructed = false;
 
   // ------------------- Initialization ------------------------
-  explicit Allocator(LinkerInitialized) : destructing(false) {}
-
+  explicit Allocator(LinkerInitialized)
+      : destructing(false), constructed(true) {}
   ~Allocator() { FinishAndPrint(); }
 
+  static void PrintCallback(const uptr Key, LockedMemInfoBlock *const &Value,
+                            void *Arg) {
+    SpinMutexLock(&Value->mutex);
+    Value->mib.Print(Key, bool(Arg));
+  }
+
   void FinishAndPrint() {
+    if (common_flags()->print_module_map)
+      DumpProcessMap();
     if (!flags()->print_terse)
       Printf("Live on exit:\n");
     allocator.ForceLock();
     allocator.ForEachChunk(
         [](uptr chunk, void *alloc) {
           u64 user_requested_size;
+          Allocator *A = (Allocator *)alloc;
           MemprofChunk *m =
-              ((Allocator *)alloc)
-                  ->GetMemprofChunk((void *)chunk, user_requested_size);
+              A->GetMemprofChunk((void *)chunk, user_requested_size);
           if (!m)
             return;
           uptr user_beg = ((uptr)m) + kChunkHeaderSize;
           u64 c = GetShadowCount(user_beg, user_requested_size);
           long curtime = GetTimestamp();
           MemInfoBlock newMIB(user_requested_size, c, m->timestamp_ms, curtime,
                               m->cpu_id, GetCpuId());
-          ((Allocator *)alloc)
-              ->MemInfoBlockTable.insertOrMerge(m->alloc_context_id, newMIB);
+          InsertOrMerge(m->alloc_context_id, newMIB, A->MIBMap);
         },
         this);
-    allocator.ForceUnlock();
 
     destructing = true;
-    MemInfoBlockTable.PrintMissRate();
-    MemInfoBlockTable.PrintAll();
+    MIBMap.ForEach(PrintCallback,
+                   reinterpret_cast<void *>(flags()->print_terse));
     StackDepotPrintAll();
+    allocator.ForceUnlock();
   }
 
   void InitLinkerInitialized() {
     SetAllocatorMayReturnNull(common_flags()->allocator_may_return_null);
     allocator.InitLinkerInitialized(
         common_flags()->allocator_release_to_os_interval_ms);
     max_user_defined_malloc_size = common_flags()->max_allocation_size_mb
                                        ? common_flags()->max_allocation_size_mb
void Deallocate(void *ptr, uptr delete_size, uptr delete_alignment,
 
     MEMPROF_FREE_HOOK(ptr);
 
     uptr chunk_beg = p - kChunkHeaderSize;
     MemprofChunk *m = reinterpret_cast<MemprofChunk *>(chunk_beg);
 
     u64 user_requested_size =
         atomic_exchange(&m->user_requested_size, 0, memory_order_acquire);
-    if (memprof_inited && memprof_init_done && !destructing &&
-        MemInfoBlockTable.Constructed) {
+    if (memprof_inited && memprof_init_done && constructed && !destructing) {
       u64 c = GetShadowCount(p, user_requested_size);
       long curtime = GetTimestamp();
 
       MemInfoBlock newMIB(user_requested_size, c, m->timestamp_ms, curtime,
                           m->cpu_id, GetCpuId());
-        MemInfoBlockTable.insertOrMerge(m->alloc_context_id, newMIB);
+      InsertOrMerge(m->alloc_context_id, newMIB, MIBMap);
     }
 
     MemprofStats &thread_stats = GetCurrentThreadStats();
     thread_stats.frees++;
     thread_stats.freed += user_requested_size;
 
     void *alloc_beg = m->AllocBeg();
     if (alloc_beg != m) {

compiler-rt/lib/memprof/memprof_flags.inc

MEMPROF_FLAG(bool, halt_on_error, true,
              "Crash the program after printing the first error report "
              "(WARNING: USE AT YOUR OWN RISK!)")
 MEMPROF_FLAG(bool, allocator_frees_and_returns_null_on_realloc_zero, true,
              "realloc(p, 0) is equivalent to free(p) by default (Same as the "
              "POSIX standard). If set to false, realloc(p, 0) will return a "
              "pointer to an allocated space which can not be used.")
 MEMPROF_FLAG(bool, print_terse, false,
              "If set, prints memory profile in a terse format.")
-
-MEMPROF_FLAG(
-    int, mem_info_cache_entries, 16381,
-    "Size in entries of the mem info block cache, should be closest prime"
-    " number to a power of two for best hashing.")
-MEMPROF_FLAG(bool, print_mem_info_cache_miss_rate, false,
-             "If set, prints the miss rate of the mem info block cache.")
-MEMPROF_FLAG(
-    bool, print_mem_info_cache_miss_rate_details, false,
-    "If set, prints detailed miss rates of the mem info block cache sets.")

compiler-rt/lib/memprof/memprof_mibmap.h

+#ifndef MEMPROF_MIBMAP_H_
+#define MEMPROF_MIBMAP_H_
+
+#include "memprof_meminfoblock.h"
+#include "sanitizer_common/sanitizer_addrhashmap.h"
+#include "sanitizer_common/sanitizer_mutex.h"
+
+namespace __memprof {
+
+struct LockedMemInfoBlock {
+  __sanitizer::StaticSpinMutex mutex;
+  MemInfoBlock mib;
+};
+
+// The MIB map stores a mapping from stack ids to MemInfoBlocks.
+typedef __sanitizer::AddrHashMap<LockedMemInfoBlock *, 200003> MIBMapTy;
+
+// Insert a new MemInfoBlock or merge with an existing block identified by the
+// stack id.
+void InsertOrMerge(const uptr Id, const MemInfoBlock &Block, MIBMapTy &Map);
+
+} // namespace __memprof
+
+#endif // MEMPROF_MIBMAP_H_

compiler-rt/lib/memprof/memprof_mibmap.cpp

+//===-- memprof_mibmap.cpp -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of MemProfiler, a memory profiler.
+//
+//===----------------------------------------------------------------------===//
+
+#include "memprof_mibmap.h"
+#include "sanitizer_common/sanitizer_allocator_internal.h"
+#include "sanitizer_common/sanitizer_mutex.h"
+
+namespace __memprof {
+
+void InsertOrMerge(const uptr Id, const MemInfoBlock &Block, MIBMapTy &Map) {
+  MIBMapTy::Handle h(&Map, static_cast<uptr>(Id), /*remove=*/false,
+                     /*create=*/true);
+  if (h.created()) {
+    LockedMemInfoBlock *lmib =
+        (LockedMemInfoBlock *)InternalAlloc(sizeof(LockedMemInfoBlock));
+    lmib->mutex.Init();
+    lmib->mib = Block;
+    *h = lmib;
+  } else {
+    LockedMemInfoBlock *lmib = *h;
+    SpinMutexLock lock(&lmib->mutex);
+    lmib->mib.Merge(Block);
+  }
+}
+
+} // namespace __memprof

compiler-rt/test/memprof/TestCases/mem_info_cache_entries.cpp

-// Check mem_info_cache_entries option.
-
-// RUN: %clangxx_memprof -O0 %s -o %t && %env_memprof_opts=log_path=stderr:mem_info_cache_entries=15:print_mem_info_cache_miss_rate=1:print_mem_info_cache_miss_rate_details=1 %run %t 2>&1 | FileCheck %s
-
-// CHECK: Set 14 miss rate: 0 / {{.*}} = 0.00%
-// CHECK-NOT: Set
-
-int main() {
-  return 0;
-}

compiler-rt/test/memprof/TestCases/memprof_merge_mib.cpp

+// RUN: %clangxx_memprof  %s -o %t
+
+// RUN: %env_memprof_opts=log_path=stdout %run %t | FileCheck %s
+
+#include <sanitizer/memprof_interface.h>
+#include <stdlib.h>
+#include <string.h>
+int main(int argc, char **argv) {
+  for (int i = 0; i < 3; i++) {
+    char *x = (char *)malloc(10);
+    if (i % 2)
+      memset(x, 0, 10);
+    else
+      memset(x, 2, 10);
+    free(x);
+  }
+  return 0;
+}
+// We should get one allocation site with alloc_count = loop trip count = 3
+// CHECK: Memory allocation stack id = [[ID:[0-9]+]]
+// CHECK-NEXT-COUNT-1: alloc_count 3
+// CHECK-COUNT-1: Stack for id {{.*}}[[ID]]
+// CHECK-NEXT-COUNT-1: memprof_malloc_linux.cpp
+// CHECK-NEXT-COUNT-1: memprof_merge_mib.cpp

compiler-rt/test/memprof/TestCases/print_miss_rate.cpp

-// Check print_mem_info_cache_miss_rate and
-// print_mem_info_cache_miss_rate_details options.
-
-// RUN: %clangxx_memprof -O0 %s -o %t
-// RUN: %env_memprof_opts=log_path=stderr:print_mem_info_cache_miss_rate=1 %run %t 2>&1 | FileCheck %s
-// RUN: %env_memprof_opts=log_path=stderr:print_mem_info_cache_miss_rate=1:print_mem_info_cache_miss_rate_details=1 %run %t 2>&1 | FileCheck %s --check-prefix=DETAILS
-
-// CHECK: Overall miss rate: 0 / {{.*}} = 0.00%
-// DETAILS: Set 0 miss rate: 0 / {{.*}} = 0.00%
-// DETAILS: Set 16380 miss rate: 0 / {{.*}} = 0.00%
-
-int main() {
-  return 0;
-}