about:memory DMD Firefox MemShrink

DMD now works on Windows

DMD is our tool for improving Firefox’s memory reporting.  It helps identify where new memory reporters need to be added in order to reduce the “heap-unclassified” value in about:memory.

DMD has always worked well on Linux, and moderately well on Mac (it is crashy for some people).  And it works on Android and B2G.  But it has never worked on Windows.

So I’m happy to report that DMD now does work on Windows, thanks to the excellent efforts of Catalin Iacob.  If you’re on Windows and you’ve been seeing high “heap-unclassified” values, and you’re able to build Firefox yourself, please give DMD a try.

2 replies on “DMD now works on Windows”

I should probably tell you this via some other channel, but I have a patch lying around that hacks^H^H^H^H^Hextends DMD to request specific allocations to be “tracked”, and then record the frees of those addresses. I found it useful for tracking down a memory leak where the ownership was passed from place to place, and I couldn’t figure out where it *was* getting freed in the nonleaking version (before my leak-introducing changes), because I hadn’t removed any frees. (It turned out that it was being handed from one RAII class instance to another, and in an error case you’d null things out in the wrong order. Or something like that.)

I don’t know if it’s generally useful. It abuses some of the DMD data structures. I guess I ought to bury it in a bug instead of in these comments.

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