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Only call mmap() on first allocation in an arena #1192

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merged 3 commits into from
Dec 19, 2024
Merged

Only call mmap() on first allocation in an arena #1192

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4c66b1f
initialize semispace on demand
stevenmeker Dec 17, 2024
3b2f36c
don't mmap() until first call to kore_arena_alloc()
stevenmeker Dec 17, 2024
2b19f98
Merge branch 'develop' into mmap_on_demand
stevenmeker Dec 17, 2024
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45 changes: 26 additions & 19 deletions include/runtime/arena.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,11 @@ size_t const HYPERBLOCK_SIZE = (size_t)BLOCK_SIZE * 1024 * 1024;
class arena {
public:
arena(char id)
: allocation_semispace_id(id) {
initialize_semispace();
}
: allocation_semispace_id(id) { }

~arena() {
munmap(current_addr_ptr, HYPERBLOCK_SIZE);
if (current_addr_ptr)
munmap(current_addr_ptr, HYPERBLOCK_SIZE);
if (collection_addr_ptr)
munmap(collection_addr_ptr, HYPERBLOCK_SIZE);
}
Expand Down Expand Up @@ -111,11 +110,12 @@ class arena {
//
// Current semispace where allocations are being made.
//
char *current_addr_ptr; // pointer to start of current address space
char *allocation_ptr; // next available location in current semispace
char *tripwire; // allocating past this triggers slow allocation
mutable size_t
num_blocks; // notional number of BLOCK_SIZE blocks in current semispace
char *current_addr_ptr = nullptr; // pointer to start of current address space
char *allocation_ptr
= nullptr; // next available location in current semispace
char *tripwire = nullptr; // allocating past this triggers slow allocation
mutable size_t num_blocks
= 0; // notional number of BLOCK_SIZE blocks in current semispace
char allocation_semispace_id; // id of current semispace
//
// Semispace where allocations will be made during and after garbage collect.
Expand Down Expand Up @@ -155,18 +155,25 @@ extern thread_local bool time_for_collection;
size_t get_gc_threshold();

inline void *arena::kore_arena_alloc(size_t requested) {
if (allocation_ptr + requested >= tripwire) {
//
// We got close to or past the last location accessed in this address range so far,
// depending on the requested size and tripwire setting. This triggers a garbage
// collect when allowed.
if (tripwire == nullptr) {
//
time_for_collection = true;
// Semispace not yet initialized.
//
// We move the tripwire to 1 past the end of our hyperblock so that we have
// a well defined comparison that will always be false until the next arena swap.
//
tripwire = current_addr_ptr + HYPERBLOCK_SIZE;
initialize_semispace();
} else if (allocation_ptr + requested >= tripwire) {
{
//
// We got close to or past the last location accessed in this address range so far,
// depending on the requested size and tripwire setting. This triggers a garbage
// collect when allowed.
//
time_for_collection = true;
//
// We move the tripwire to 1 past the end of our hyperblock so that we have
// a well defined comparison that will always be false until the next arena swap.
//
tripwire = current_addr_ptr + HYPERBLOCK_SIZE;
}
}
void *result = allocation_ptr;
allocation_ptr += requested;
Expand Down
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