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heaptrace

heaptrace is a tool that collects and reports heap allocated memory.

Approach

heaptrace uses widely used LD_PRELOAD technique to trace memory allocation of the target program.

It doesn't explicitly detect memory leak, but it provides heap allocation status information that might be a useful hint to find memory leaks.

It provides allocation info for each allocation point and it includes:

  • backtrace : allocation point and its backtrace (default depth is 8)
  • count/peak: total allocation count and its peak count
  • size/peak : total allocation size and its peak size
  • age : the duration time since the backtrace was created
  • summary : general memory allocation summary

Build and installation

heaptrace can be simply compiled as follows:

$ make

The backtrace depth can be changed with a build flag DEPTH as follows:

# make DEPTH=30

Then heaptrace keeps maximum 30 of backtrace depth when tracing.

How to use heaptrace

It provides a convenience wrapper program instread of using LD_PRELOAD explicitly as follows:

$ heaptrace [<program>]

It traces memory allocation of the target program and dump the memory allocation status when program is finished. If every memory allocation is properly deallocated, then it doesn't print anything.

There are some options as follows:

      --flame-graph          Print heap trace info in flamegraph format
      --outfile=FILE         Save log messages to this file
  -s, --sort=KEY             Sort backtraces based on KEY (size or count)
      --top=NUM              Set number of top backtraces to show (default 10)

Here is an example usage of heaptrace. It traces memory allocation of the target program node, then prints currently live allocation info based on each backtrace of allocation. It shows that some of the allocated objects are not deallocated until the program is finished.

$ heaptrace --top 3 --sort count /usr/bin/node --expose-gc -e 'gc()'
[heaptrace] initialized for /proc/5879/maps
[heaptrace] finalized for /proc/5879/maps
=================================================================
[heaptrace] dump allocation status for /proc/5879/maps (node)
=== backtrace #1 === [count/peak: 43/60] [size/peak: 22.704 KB/31.680 KB] [age: 6.236 ms]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf2e57d] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointer(v8::internal::Root, char const*, v8::internal::Objec... +0x1b
 4 [     0x121c32d] v8::internal::SerializerDeserializer::Iterate(v8::internal::Isolate*, v8::internal::RootVisitor*) +0x47
 5 [      0xf07e45] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0x91
 6 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 7 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4

=== backtrace #2 === [count/peak: 12/13] [size/peak: 6.336 KB/6.864 KB] [age: 6.400 ms]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf29dd4] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointers(v8::internal::Root, char const*, v8::internal::Obje... +0x29
 4 [      0xb27068] v8::internal::HandleScopeImplementer::IterateThis(v8::internal::RootVisitor*) +0x1e
 5 [      0xf07d33] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0x4c
 6 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 7 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4

=== backtrace #3 === [count/peak: 10/10] [size/peak: 5.280 KB/5.280 KB] [age: 6.322 ms]
 0 [0x7fe72e46476c] malloc +0x1b
 1 [0x7fe72dd61e78] operator new(unsigned long) +0x6
 2 [      0xf27811] /usr/bin/node (+0xf27811)
 3 [      0xf2e57d] v8::internal::MarkCompactCollector::RootMarkingVisitor::VisitRootPointer(v8::internal::Root, char const*, v8::internal::Objec... +0x1b
 4 [      0xf07f08] v8::internal::Heap::IterateStrongRoots(v8::internal::RootVisitor*, v8::internal::VisitMode) +0xc2
 5 [      0xf40b6b] v8::internal::MarkCompactCollector::MarkLiveObjects() +0x72
 6 [      0xf42071] v8::internal::MarkCompactCollector::CollectGarbage() +0x4
 7 [      0xf15621] v8::internal::Heap::MarkCompact() +0x28

[heaptrace] heap traced num of backtrace : 64
[heaptrace] heap traced allocation size  : 59.215 KB
[heaptrace] allocator info (virtual)     : 2.121 MB
[heaptrace] allocator info (resident)    : 414.288 KB
[heaptrace] statm info (VSS/RSS/shared)  : 134.201 MB / 40.960 KB / 0 bytes
=================================================================

It can also dump allocation status when it receives a signal as follows:

  • SIGUSR1: dump the current allocation status with sort order by "size"
  • SIGUSR2: dump the current allocation status with sort order by "count"

It can be useful for long running programs.