Comment #2 on issue 180 by petef4: HEAP_PROFILE_MMAP reports allocations
twice
http://code.google.com/p/google-perftools/issues/detail?id=180
Calls to mmap from the program under test is not an issue. The problem is
when a
regular new or malloc causes TCMalloc to acquire memory pages.
#include <memory>
#include <google/heap-profiler.h>
class Alloc20MiB {
char* buffer;
public:
Alloc20MiB() {
buffer = new char[20 * 1024 * 1024];
}
~Alloc20MiB() {
delete[] buffer;
}
};
int main(int argc, char* argv[]) {
const char* name = argc > 1 ? argv[1] : "default";
HeapProfilerStart(name);
std::auto_ptr<Alloc20MiB> m0(new Alloc20MiB());
HeapProfilerDump("about to make 2nd object");
std::auto_ptr<Alloc20MiB> m1(new Alloc20MiB());
HeapProfilerDump("about to exit");
}
The .0001 profile has the correct results.
Total: 20.0 MB
20.0 100.0% 100.0% 20.0 100.0% Alloc20MiB::Alloc20MiB
0.0 0.0% 100.0% 20.0 100.0% main
0.0 0.0% 100.0% 20.0 100.0% __libc_start_main
0.0 0.0% 100.0% 20.0 100.0% _start
When the program is run with HEAP_PROFILE_MMAP=true then extra memory usage
is
erroneously reported and .0001 now looks like this.
Total: 41.9 MB
20.0 47.7% 47.7% 40.1 95.5% Alloc20MiB::Alloc20MiB
20.0 47.7% 95.4% 20.0 47.7% SbrkSysAllocator::Alloc
1.9 4.6% 100.0% 1.9 4.6% DoAllocWithArena
0.0 0.0% 100.0% 41.9 100.0% main
0.0 0.0% 100.0% 20.0 47.7% ::cpp_alloc
0.0 0.0% 100.0% 0.1 0.1% AddressMap::FindCluster
0.0 0.0% 100.0% 0.1 0.1% AddressMap::Insert
0.0 0.0% 100.0% 0.1 0.1% AddressMap::New
0.0 0.0% 100.0% 0.7 1.6% HeapProfileTable::HeapProfileTable
0.0 0.0% 100.0% 0.1 0.1% HeapProfileTable::RecordAlloc
0.0 0.0% 100.0% 0.1 0.1%
HeapProfileTable::RecordAllocWithStack
0.0 0.0% 100.0% 1.9 4.5% HeapProfilerStart
0.0 0.0% 100.0% 1.9 4.6% LowLevelAlloc::AllocWithArena
0.0 0.0% 100.0% 0.1 0.1% LowLevelAlloc::NewArena
0.0 0.0% 100.0% 0.1 0.1% MallocHook::InvokeNewHook
0.0 0.0% 100.0% 0.1 0.1% MemoryRegionMap::DoInsertRegionLocked
0.0 0.0% 100.0% 0.1 0.1%
MemoryRegionMap::HandleSavedRegionsLocked
0.0 0.0% 100.0% 0.1 0.3% MemoryRegionMap::Init
0.0 0.0% 100.0% 0.1 0.1% MemoryRegionMap::InsertRegionLocked
0.0 0.0% 100.0% 0.1 0.1%
MemoryRegionMap::MyAllocator::Allocate
0.0 0.0% 100.0% 0.1 0.1% NewHook
0.0 0.0% 100.0% 1.8 4.3% ProfilerMalloc
0.0 0.0% 100.0% 0.1 0.1% RecordAlloc
0.0 0.0% 100.0% 0.1 0.1% STL_Allocator::allocate
0.0 0.0% 100.0% 41.9 100.0% __libc_start_main
0.0 0.0% 100.0% 41.9 100.0% _start
0.0 0.0% 100.0% 0.1 0.1% std::_Rb_tree::_M_create_node
0.0 0.0% 100.0% 0.1 0.1% std::_Rb_tree::_M_get_node
0.0 0.0% 100.0% 0.1 0.1% std::_Rb_tree::_M_insert
0.0 0.0% 100.0% 0.1 0.1% std::_Rb_tree::insert_unique
0.0 0.0% 100.0% 0.1 0.1% std::set::insert
The latter report can be partially cleaned up with
--ignore='DoAllocWithArena|
SbrkSysAllocator::Alloc'
Total: 41.9 MB
20.0 47.7% 47.7% 20.0 47.7% Alloc20MiB::Alloc20MiB
0.0 0.0% 47.7% 20.0 47.7% main
0.0 0.0% 47.7% 20.0 47.7% __libc_start_main
0.0 0.0% 47.7% 20.0 47.7% _start
I don't have the time to attempt a fix myself. I think that what needs to
be done
is for TCMalloc's allocators to call __sbrk rather than the sbrk version
with hooks.
In a similar manner do_mmap and co. should be called to avoid the mmap
hooks.
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