Features/MemoryDebuggingTools

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== Detailed Description ==
 
== Detailed Description ==
 
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<!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->
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The new "gdb-heap" package adds a new "heap" command to /usr/bin/gdb. 
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The command allows you to get a breakdown of how that process is using dynamic memory.
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It allows for ''unplanned'' memory usage debugging: if a process unexpectedly starts using large amounts of memory you can attach to it with gdb, and use the heap command to figure out where the memory is going. You should also be able to use it on core dumps.
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We believe this approach is entirely new, and is unique to Fedora 14.
  
 
== Benefit to Fedora ==
 
== Benefit to Fedora ==

Revision as of 19:43, 12 July 2010


Contents

Memory Debugging Tools

Summary

The gdb debugger has been extended with new commands that make it easier to track down and fix excessive memory usage within programs and libraries.

This functionality was created by Fedora contributor David Malcolm, and we believe it is unique to Fedora.

Owner

  • Email: <dmalcolm@redhat.com>

Current status

  • Targeted release: Fedora 21
  • Last updated: 2010-07-08
  • Percentage of completion: 20%

Preparing upstream project for initial launch: https://fedorahosted.org/gdb-heap/

Initial version of code uploaded

Upstream tickets:


Detailed Description

The new "gdb-heap" package adds a new "heap" command to /usr/bin/gdb.

The command allows you to get a breakdown of how that process is using dynamic memory.

It allows for unplanned memory usage debugging: if a process unexpectedly starts using large amounts of memory you can attach to it with gdb, and use the heap command to figure out where the memory is going. You should also be able to use it on core dumps.

We believe this approach is entirely new, and is unique to Fedora 14.

Benefit to Fedora

This feature could be of great use to developers and system administrators: it provides a new way of analyzing how a process uses memory, without requiring advance planning.

It is unique to Fedora (it makes heavy use of the gdb/python integration we have in Fedora), and was developed by a Fedora contributor (who is a Red Hat engineer).

Scope

How To Test

No special hardware is needed.

You will need to install the gdb-heap package (not yet packaged)

Exploratory testing

  • Pick a process on your system (either as root, or one of your own processes)
  • Use "gdb attach PID" to connect to it
  • Use python import heap to register the "heap" command
  • Use the "heap" command and its various subcommands (as described on the upstream website)
  • Ensure that all results look correct, and that there are no Python tracebacks within gdb.

Ideally the amount of "uncategorized" data should not be a substantial proportion of the overall size of the dynamically-allocated memory; if it is, then that may be a bug.

User Experience

Dependencies

There's a baseline of functionality that I'm developing on top of Fedora 13's gdb.

Some features require additional work in gdb, which I've filed RFE bugs for. Naturally this will require coordination with gdb to ensure that they land in Fedora 14:

  • RHBZ #610241: RFE: please expose "info symbol ADDRESS" in the python API
  • RHBZ #610249: RFE: notification about changes in the inferior process


Contingency Plan

None necessary, simply remove the package

Documentation

Release Notes

Comments and Discussion