Re: massif & counts per type

Hi,

> > How can I obtain the number of mallocs per type in a time-frame using
> > massif? I'm NOT interested in the total in use, I would like to know how
> > often type x is allocated between t+1 and t+2.
> 
> To my knowledge, this data is not recorded by Massif. You could try to have a 
> look at heaptrack [1] instead.
> 
> [1]: https://invent.kde.org/sdk/heaptrack
> 
> Note though that on Linux, malloc does not retain any type information. As 
> such, even with heaptrack you cannot easily filter by type. But by leveraging 
> the flamegraph you can often still get a similar intuition based on the 
> callstacks. I have an idea to parse the callstack code lines to find type 
> information from the call to `new` but that's probably quite hairy to get 
> right in practice. Suggestions welcome on how to trace the type information!
> 
> And finally, with heaptrack it is also not yet easily doable to get a diff 
> between two time stamps. Also a feature I've long thought about implementing, 
> but never got around to...

This morning I came up with an other solution: I made a LD_PRELOAD
wrapper which counts every malloc-call. Decided that allocated-type is
not really required in my case, but to know which malloc did it would
work as well.
So in malloc() I do __builtin_return_address(0), hash the pointer and
use that as an index in array of counters.

Gives me:

pointer          count
...
000000000041db10 00000000002a427
00007ffff4a6c1b1 00000000007f1da

Going from 000000000041db10 to a symbol works fine, the shared library
(00007ffff4a6c1b1) is a bit troublesome though (disabled
randomize_va_space and using eu-addr2line).



Folkert van Heusden

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