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mycpp: add 128B pool #1958

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mycpp: add 128B pool #1958

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900b26a
mycpp: add 128B pool
melvinw May 2, 2024
e935d28
Merge branch 'master' into pool3
Jul 20, 2024
3a6f7ef
Merge branch 'master' into pool3
Nov 12, 2024
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17 changes: 15 additions & 2 deletions mycpp/mark_sweep_heap.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,10 @@ void* MarkSweepHeap::Allocate(size_t num_bytes, int* obj_id, int* pool_id) {
*pool_id = 2;
return pool2_.Allocate(obj_id);
}
if (num_bytes <= pool3_.kMaxObjSize) {
*pool_id = 3;
return pool3_.Allocate(obj_id);
}
*pool_id = 0; // malloc(), not a pool
#endif

Expand Down Expand Up @@ -148,6 +152,11 @@ void MarkSweepHeap::MaybeMarkAndPush(RawObject* obj) {
return;
}
pool2_.Mark(obj_id);
} else if (header->pool_id == 3) {
if (pool3_.IsMarked(obj_id)) {
return;
}
pool3_.Mark(obj_id);
} else
#endif
{
Expand Down Expand Up @@ -215,6 +224,7 @@ void MarkSweepHeap::Sweep() {
#ifndef NO_POOL_ALLOC
pool1_.Sweep();
pool2_.Sweep();
pool3_.Sweep();
#endif

int last_live_index = 0;
Expand Down Expand Up @@ -263,6 +273,7 @@ int MarkSweepHeap::Collect() {
#ifndef NO_POOL_ALLOC
pool1_.PrepareForGc();
pool2_.PrepareForGc();
pool3_.PrepareForGc();
#endif

// Mark roots.
Expand Down Expand Up @@ -335,7 +346,7 @@ void MarkSweepHeap::PrintStats(int fd) {

#ifndef NO_POOL_ALLOC
dprintf(fd, " num allocated = %10d\n",
num_allocated_ + pool1_.num_allocated() + pool2_.num_allocated());
num_allocated_ + pool1_.num_allocated() + pool2_.num_allocated() + pool3_.num_allocated());
dprintf(fd, " num in heap = %10d\n", num_allocated_);
#else
dprintf(fd, " num allocated = %10d\n", num_allocated_);
Expand All @@ -344,9 +355,10 @@ void MarkSweepHeap::PrintStats(int fd) {
#ifndef NO_POOL_ALLOC
dprintf(fd, " num in pool 1 = %10d\n", pool1_.num_allocated());
dprintf(fd, " num in pool 2 = %10d\n", pool2_.num_allocated());
dprintf(fd, " num in pool 3 = %10d\n", pool3_.num_allocated());
dprintf(
fd, "bytes allocated = %10" PRId64 "\n",
bytes_allocated_ + pool1_.bytes_allocated() + pool2_.bytes_allocated());
bytes_allocated_ + pool1_.bytes_allocated() + pool2_.bytes_allocated() + pool3_.bytes_allocated());
#else
dprintf(fd, "bytes allocated = %10" PRId64 "\n", bytes_allocated_);
#endif
Expand Down Expand Up @@ -404,6 +416,7 @@ void MarkSweepHeap::FreeEverything() {
#ifndef NO_POOL_ALLOC
pool1_.Free();
pool2_.Free();
pool3_.Free();
#endif
}

Expand Down
4 changes: 3 additions & 1 deletion mycpp/mark_sweep_heap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -231,7 +231,7 @@ class MarkSweepHeap {
int num_live() {
return num_live_
#ifndef NO_POOL_ALLOC
+ pool1_.num_live() + pool2_.num_live()
+ pool1_.num_live() + pool2_.num_live() + pool3_.num_live()
#endif
;
}
Expand Down Expand Up @@ -265,10 +265,12 @@ class MarkSweepHeap {
#ifndef NO_POOL_ALLOC
// 16,384 / 24 bytes = 682 cells (rounded), 16,368 bytes
// 16,384 / 48 bytes = 341 cells (rounded), 16,368 bytes
// 16,384 / 96 bytes = 171 cells (rounded), 16,368 bytes
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Hm this still says 96

I kinda want to do some evaluation, make sure it's not over-tuned for Linux / glibc / 64-bit

And does this waste memory on any workloads?

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Also I think we had the theory again that malloc() needed some slack, to be strictly less than 16,384 bytes, to allow for headers

But I guess we never measured that effect

We already run on many different libc with different malloc(), so yeah I think we can at least survey Alpine Linux

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Oh whoops. That's a typo leftover from a previous version. Will fix.

Happy to leave this open until we have a better idea of the effect with different allocators. I suspect that it will be a win in most cases, though. Since the write to the allocation header (whether it's below the buffer or elsewhere) is going to cause page faults (the reduction of which was the main win from this) regardless.

// Conveniently, the glibc malloc header is 16 bytes, giving exactly 16 Ki
// differences
Pool<682, 24> pool1_;
Pool<341, 48> pool2_;
Pool<128, 128> pool3_;
#endif

std::vector<RawObject**> roots_;
Expand Down
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