node-mtrace
Native memory tracing and mtrace log parsing for node.
Supported Platforms
Linux only.
Usage
Install with npm:
npm install mtrace
Generating a mtrace:
var mtrace = require('mtrace');
var filename = mtrace.mtrace();
if (filename) {
console.log('Saving mtrace to ' + filename);
} else {
console.log('mtrace not supported');
}
// do stuff
// exit program, or, force a flush
mtrace.gc(); // Optionally force a garbage collect so destructors are called
mtrace.muntrace();
// start tracing again
mtrace.mtrace();mtrace() takes an optional parameter to specify a filename to save to, otherwise it generates a unique filename based on process pid and call count (first file is "mtrace.[pid].0", etc).
Viewing the mtrace log
There's a built-in command line tool that's part of GCC called mtrace. I find its output rather uselss in any real-world application (lists thousands or millions of allocations in an unsorted list, and has meager symbol lookup). Your mileage on this may vary.
The raw log can however sometimes be very useful for tracking harder to identify allocations (like those that show up as just "operator new" from C++ files) by looking at allocation sizes and patterns and comparing them to known structure sizes, etc.
This module includes a simple little parser to generate summarized information showing useful high-level information on outstanding allocations. The "Traffic" column indicates total alloc/free events from that call site, which can be useful for tracking performance-impacting heap thrashing.
$ ./node_modules/.bin/mtrace.js mtrace.1234.0
Addr Size Count Traffic Module Symbol Offs
--------- --------- ----- ------- -------------------------------- ------------------------------------------------ ------
0xd0c080 15 bytes 1 197 /lib/tls/i686/cmov/libc.so.6 __strdup +0x30
0x84573f4 100 bytes 1 391 node eio_custom +0x1a
0x341fda 120 bytes 6 6 ...les/native/bullet/bullet.node _ZN13PhysicsEntity16addCollisionMeshER11btTra... +0x5e
0x844bd10 296 bytes 2 2 node und...
0x840ddaf 9.43 KB 2 1024 node _ZN2v88internal8Malloced3NewEj +0xf
0x34200d 13.59 KB 6 6 ...les/native/bullet/bullet.node _ZN13PhysicsEntity16addCollisionMeshER11btTra... +0x91
0x341ff1 54.38 KB 6 6 ...les/native/bullet/bullet.node _ZN13PhysicsEntity16addCollisionMeshER11btTra... +0x75
0x2c8c07 3.03 MB 8976 59094 /usr/lib/libstdc++.so.6 _Znwj +0x27
0x3c7bad 81.15 MB 10915 28901 ...les/native/bullet/bullet.node und...
--------- --------- ----- ------- -------------------------------- ------------------------------------------------ ------
TOTALS 84.25 MB 19915 90195
Or, even better, if the process the mtrace was dumped from is still running, we can get very accurate symbol information by specifying a pid:
$ ./node_modules/.bin/mtrace.js mtrace.1234.0 1234
Addr Size Count Traffic Module Symbol
--------- --------- ----- ------- -------------------------------- ------------------------------------------------
0xd0c080 15 bytes 1 197 /lib/tls/i686/cmov/libc.so.6 strdup
0x84573f4 100 bytes 1 391 node eio_custom
0x341fda 120 bytes 6 6 ...les/native/bullet/bullet.node PhysicsEntity::addCollisionMesh(btTransform&,...
0x844bd10 296 bytes 2 2 node ev_realloc_emul
0x840ddaf 9.43 KB 2 1024 node v8::internal::Malloced::New(unsigned int)
0x34200d 13.59 KB 6 6 ...les/native/bullet/bullet.node PhysicsEntity::addCollisionMesh(btTransform&,...
0x341ff1 54.38 KB 6 6 ...les/native/bullet/bullet.node PhysicsEntity::addCollisionMesh(btTransform&,...
0x2c8c07 3.03 MB 8976 59094 /usr/lib/libstdc++.so.6 operator new(unsigned int)
0x3c7bad 81.15 MB 10915 28901 ...les/native/bullet/bullet.node btAllocDefault(unsigned int)
--------- --------- ----- ------- -------------------------------- ------------------------------------------------
TOTALS 84.25 MB 19915 90195
If you want to use this module's sweet mtrace parsing functionality but not for a node app, just change the one reference to "node" in mtrace.js (one of the arguments to gdb) to your executable, or let me know and I can make it take it as a parameter.
Requirements
Tested on Ubuntu, should work on any flavor of Linux.
Requires gdb to be installed to get good symbol information.
Special Thanks
Uses easy-table.
Initial NPM packaging by christopherobin.