[petsc-users] Still reachable memory in valgrind
Barry Smith
bsmith at petsc.dev
Tue Oct 12 09:51:57 CDT 2021
Do you have the valgrind output from 3.14 ?
> 1,636 bytes in 1 blocks are still reachable in loss record 4
> > of 4
> > ==2036== at 0x4C2BE2D: memalign (vg_replace_malloc.c:858)
> > ==2036== by 0x54AC0CB: PetscMallocAlign (mal.c:54)
> > ==2036== by 0x54AFBA9: PetscTrMallocDefault (mtr.c:183)
> > ==2036== by 0x54ADDD2: PetscMallocA (mal.c:423)
> > ==2036== by 0x41A52F: main (main.c:9)
> > ==2036==
Given the large amount of memory in the block I think tracing of PETSc's memory allocation is turned on with this run, this may mean the memory is reachable but with your 3.14 run I would guess the memory size is 8 bytes and tracing is not turned on so the memory is listed as "lost". But I do not understand the subtleties of reachable.
Barry
> On Oct 12, 2021, at 10:38 AM, Pierre Seize <Pierre.Seize at onera.fr> wrote:
>
> The "bug" is that memory from PetscMalloc1 that is not freed is reported as "definitely lost" in v3.14 (OK) but as "still reachable" in today's release (not OK).
>
> Here I forget to free the memory on purpose, I would like valgrind to report it's lost and not still reachable.
>
>
>
> Pierre
>
>
> On 12/10/21 16:24, Matthew Knepley wrote:
>> On Tue, Oct 12, 2021 at 10:16 AM Pierre Seize <pierre.seize at onera.fr <mailto:pierre.seize at onera.fr>> wrote:
>> Sorry, I should have tried this before:
>>
>> I checked out to v3.14, and now both malloc and PetscMalloc1 are
>> reported as definitely lost, so I would say it's a bug.
>>
>> I am not sure what would be the bug. This is correctly reporting that you did not free the memory.
>>
>> Thanks,
>>
>> Matt
>>
>> Pierre
>>
>>
>> On 12/10/21 15:58, Pierre Seize wrote:
>> > Hello petsc-users
>> >
>> > I am using Valgrind with my PETSc application, and I noticed something:
>> >
>> > 1 #include <petscsys.h>
>> > 2
>> > 3 int main(int argc, char **argv){
>> > 4 PetscErrorCode ierr = 0;
>> > 5
>> > 6 ierr = PetscInitialize(&argc, &argv, NULL, ""); if (ierr) return
>> > ierr;
>> > 7 PetscReal *foo;
>> > 8 malloc(sizeof(PetscReal));
>> > 9 ierr = PetscMalloc1(1, &foo); CHKERRQ(ierr);
>> > 10 ierr = PetscFinalize();
>> > 11 return ierr;
>> > 12 }
>> >
>> > With this example, with today's release branch, I've got this Valgrind
>> > result (--leak-check=full --show-leak-kinds=all):
>> >
>> > ==2036== Memcheck, a memory error detector
>> > ==2036== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
>> > ==2036== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright
>> > info
>> > ==2036== Command: ./build/bin/yanss data/box.yaml
>> > ==2036==
>> > ==2036==
>> > ==2036== HEAP SUMMARY:
>> > ==2036== in use at exit: 1,746 bytes in 4 blocks
>> > ==2036== total heap usage: 2,172 allocs, 2,168 frees, 9,624,690
>> > bytes allocated
>> > ==2036==
>> > ==2036== 8 bytes in 1 blocks are definitely lost in loss record 1 of 4
>> > ==2036== at 0x4C29BE3: malloc (vg_replace_malloc.c:299)
>> > ==2036== by 0x41A4FD: main (main.c:8)
>> > ==2036==
>> > ==2036== 32 bytes in 1 blocks are still reachable in loss record 2 of 4
>> > ==2036== at 0x4C2B975: calloc (vg_replace_malloc.c:711)
>> > ==2036== by 0xACF461F: _dlerror_run (in /usr/lib64/libdl-2.17.so <http://libdl-2.17.so/>)
>> > ==2036== by 0xACF4127: dlsym (in /usr/lib64/libdl-2.17.so <http://libdl-2.17.so/>)
>> > ==2036== by 0x56ECBB5: PetscInitialize_Common (pinit.c:785)
>> > ==2036== by 0x56EF325: PetscInitialize (pinit.c:1203)
>> > ==2036== by 0x41A4E2: main (main.c:6)
>> > ==2036==
>> > ==2036== 70 bytes in 1 blocks are still reachable in loss record 3 of 4
>> > ==2036== at 0x4C29BE3: malloc (vg_replace_malloc.c:299)
>> > ==2036== by 0x400F0D0: _dl_signal_error (in /usr/lib64/ld-2.17.so <http://ld-2.17.so/>)
>> > ==2036== by 0x400F26D: _dl_signal_cerror (in /usr/lib64/ld-2.17.so <http://ld-2.17.so/>)
>> > ==2036== by 0x400A4BC: _dl_lookup_symbol_x (in /usr/lib64/ld-2.17.so <http://ld-2.17.so/>)
>> > ==2036== by 0x83B9F02: do_sym (in /usr/lib64/libc-2.17.so <http://libc-2.17.so/>)
>> > ==2036== by 0xACF40D3: dlsym_doit (in /usr/lib64/libdl-2.17.so <http://libdl-2.17.so/>)
>> > ==2036== by 0x400F2D3: _dl_catch_error (in /usr/lib64/ld-2.17.so <http://ld-2.17.so/>)
>> > ==2036== by 0xACF45BC: _dlerror_run (in /usr/lib64/libdl-2.17.so <http://libdl-2.17.so/>)
>> > ==2036== by 0xACF4127: dlsym (in /usr/lib64/libdl-2.17.so <http://libdl-2.17.so/>)
>> > ==2036== by 0x56ECBB5: PetscInitialize_Common (pinit.c:785)
>> > ==2036== by 0x56EF325: PetscInitialize (pinit.c:1203)
>> > ==2036== by 0x41A4E2: main (main.c:6)
>> > ==2036==
>> > ==2036== 1,636 bytes in 1 blocks are still reachable in loss record 4
>> > of 4
>> > ==2036== at 0x4C2BE2D: memalign (vg_replace_malloc.c:858)
>> > ==2036== by 0x54AC0CB: PetscMallocAlign (mal.c:54)
>> > ==2036== by 0x54AFBA9: PetscTrMallocDefault (mtr.c:183)
>> > ==2036== by 0x54ADDD2: PetscMallocA (mal.c:423)
>> > ==2036== by 0x41A52F: main (main.c:9)
>> > ==2036==
>> > ==2036== LEAK SUMMARY:
>> > ==2036== definitely lost: 8 bytes in 1 blocks
>> > ==2036== indirectly lost: 0 bytes in 0 blocks
>> > ==2036== possibly lost: 0 bytes in 0 blocks
>> > ==2036== still reachable: 1,738 bytes in 3 blocks
>> > ==2036== suppressed: 0 bytes in 0 blocks
>> > ==2036==
>> > ==2036== For counts of detected and suppressed errors, rerun with: -v
>> > ==2036== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
>> >
>> >
>> > The first report is the malloc on line 8, fine.
>> > The second and the third correspond to still reachable memory from
>> > PetscInitialize on line 6, I often got these so I usually discard it.
>> > The fourth and last is the one that worries me : the memory from
>> > PetscMalloc1 on line 9 is reported as "still reachable", but I don't
>> > think it should.
>> > Is there something I do not understand, or is this a bug ?
>> >
>> > Thanks in advance,
>> >
>> > Pierre
>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
>> -- Norbert Wiener
>>
>> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/%7Eknepley/>
>
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