Hi,
I wanted to debug where my program uses the most memory. (There are no
memory leaks, but I want to optimize memory usage on some large inputs.
As the code is quite large, simply guessing which part is responsible
becomes quite hard :) In the past, I happily used valgrind's massif tool
for such job, and it worked like a charm. But now, FPC 2.6.0 with
valgrind 3.7.0, it seems valgrind/massif has problems:
$ fpc -gv trivial_alloc.pas
$ valgrind --tool=massif ./trivial_alloc
....
--7286-- VALGRIND INTERNAL ERROR: Valgrind received a signal 11
(SIGSEGV) - exiting
--7286-- si_code=1; Faulting address: 0xFFFFFFF7; sp: 0x6298914c
valgrind: the 'impossible' happened:
Killed by fatal signal
(Full output and trivial_alloc.pas attached.)
The code is compiled with -gv option. It works very fine with valgrind's
callgrind tool. So I suspect this is a problem with valgrind,
specifically massif, not related to FPC. Also, it seems to fail the same
way with older/newer FPC versions (I tried 2.2.4, 2.4.4, 2.6.0, and
2.7.1 from today 2012-05-11). Probably, some valgrind version broke
massif for FPC binaries.
So, questions:
1. I want to report this as massif's bug. Any ideas what more
information should I provide to valgrind's developers? I don't know if
they are familiar with FPC. And simple C examples work fine, so it's
probably something specific in FPC binaries.
- Maybe this problem is already reported?
- Maybe there's a workaround? IOW, can someone successfully use massif
with FPC programs?
2. Is there any other reliable memory profiler for FPC? As you can swap
memory manager in Pascal, and FPC can give you a backtrace, I suppose
it's quite possible to just write a unit that works between your program
and standard memory manager, and tracks memory usage this way. This will
only measure memory use of Pascal code (external libs don't go through
FPC memory manager), but that would be very fine for me --- I know
(well, I'm 99% sure) that my Pascal code is the main memory eater here.
I didn't find any (good and maintained) memory profiler mentioned on
http://wiki.lazarus.freepascal.org/Profiling#Memory_Profiling . (I tried
FpProfiler, but it depends on inserting instrumentation code into Pascal
sources. That's actually a very nice idea, but it means it's closely
tied to what fcl-passrc can handle. And current fcl-passrc still lacks a
couple of features (reported). Also FpProfiler seems to use an older,
local fcl-passrc version.)
Thanks,
Michalis
==7310== Massif, a heap profiler
==7310== Copyright (C) 2003-2011, and GNU GPL'd, by Nicholas Nethercote
==7310== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==7310== Command: ./trivial_alloc
==7310==
--7310-- VALGRIND INTERNAL ERROR: Valgrind received a signal 11 (SIGSEGV) -
exiting
--7310-- si_code=1; Faulting address: 0xFFFFFFF7; sp: 0x627fb14c
valgrind: the 'impossible' happened:
Killed by fatal signal
==7310== at 0x38028524: ??? (in /usr/lib/valgrind/massif-x86-linux)
==7310== by 0x38060AB6: ??? (in /usr/lib/valgrind/massif-x86-linux)
==7310== by 0x380635FD: ??? (in /usr/lib/valgrind/massif-x86-linux)
==7310== by 0x38024CA2: ??? (in /usr/lib/valgrind/massif-x86-linux)
==7310== by 0x38025542: ??? (in /usr/lib/valgrind/massif-x86-linux)
==7310== by 0x3807560D: ??? (in /usr/lib/valgrind/massif-x86-linux)
sched status:
running_tid=1
Thread 1: status = VgTs_Runnable
==7310== at 0x402428C: free (in
/usr/lib/valgrind/vgpreload_massif-x86-linux.so)
==7310== by 0x416D4C4: __libc_freeres (in
/lib/i386-linux-gnu/i686/cmov/libc-2.13.so)
==7310== by 0x4020466: _vgnU_freeres (in
/usr/lib/valgrind/vgpreload_core-x86-linux.so)
==7310== by 0x805F113: SYSTEM_SYSTEM_EXIT (in /tmp/trivial_alloc)
==7310== by 0x8058819: SYSTEM_DO_EXIT (in /tmp/trivial_alloc)
==7310== by 0x805FA66: SI_PRC__FPC_PROC_START (in /tmp/trivial_alloc)
Note: see also the FAQ in the source distribution.
It contains workarounds to several common problems.
In particular, if Valgrind aborted or crashed after
identifying problems in your program, there's a good chance
that fixing those problems will prevent Valgrind aborting or
crashing, especially if it happened in m_mallocfree.c.
If that doesn't help, please report this bug to: www.valgrind.org
In the bug report, send all the above text, the valgrind
version, and what OS and version you are using. Thanks.
var
P: Pointer;
begin
P := GetMem(1000);
end.
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