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Avoid calling mmtk_gc_poll frequently #20

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merged 1 commit into from
Jul 2, 2023
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Avoid calling mmtk_gc_poll frequently #20

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1 change: 1 addition & 0 deletions src/julia_threads.h
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Original file line number Diff line number Diff line change
Expand Up @@ -283,6 +283,7 @@ typedef struct _jl_tls_states_t {

#ifdef MMTK_GC
MMTkMutatorContext mmtk_mutator;
size_t malloc_sz_since_last_poll;
#endif

// some hidden state (usually just because we don't have the type's size declaration)
Expand Down
28 changes: 24 additions & 4 deletions src/mmtk-gc.c
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Expand Up @@ -33,7 +33,24 @@ JL_DLLEXPORT void jl_gc_set_cb_notify_external_free(jl_gc_cb_notify_external_fre

inline void maybe_collect(jl_ptls_t ptls)
{
mmtk_gc_poll(ptls);
// Just do a safe point for general maybe_collect
jl_gc_safepoint_(ptls);
}

// This is only used for malloc. We need to know if we need to do GC. However, keeping checking with MMTk (mmtk_gc_poll),
// is expensive. So we only check for every few allocations.
static inline void malloc_maybe_collect(jl_ptls_t ptls, size_t sz)
{
// We do not need to carefully maintain malloc_sz_since_last_poll. We just need to
// avoid using mmtk_gc_poll too frequently, and try to be precise on our heap usage
// as much as we can.
if (ptls->malloc_sz_since_last_poll > 4096) {
jl_atomic_store_relaxed(&ptls->malloc_sz_since_last_poll, 0);
mmtk_gc_poll(ptls);
} else {
jl_atomic_fetch_add_relaxed(&ptls->malloc_sz_since_last_poll, sz);
jl_gc_safepoint_(ptls);
}
}


Expand Down Expand Up @@ -266,6 +283,9 @@ void jl_init_thread_heap(jl_ptls_t ptls)
memset(&ptls->gc_num, 0, sizeof(ptls->gc_num));
jl_atomic_store_relaxed(&ptls->gc_num.allocd, -(int64_t)gc_num.interval);

// Clear the malloc sz count
jl_atomic_store_relaxed(&ptls->malloc_sz_since_last_poll, 0);

// Create mutator
MMTk_Mutator mmtk_mutator = mmtk_bind_mutator((void *)ptls, ptls->tid);
// Copy the mutator to the thread local storage
Expand Down Expand Up @@ -363,7 +383,7 @@ JL_DLLEXPORT void *jl_gc_counted_malloc(size_t sz)
jl_task_t *ct = jl_current_task;
if (pgcstack && ct->world_age) {
jl_ptls_t ptls = ct->ptls;
maybe_collect(ptls);
malloc_maybe_collect(ptls, sz);
jl_atomic_store_relaxed(&ptls->gc_num.allocd,
jl_atomic_load_relaxed(&ptls->gc_num.allocd) + sz);
jl_atomic_store_relaxed(&ptls->gc_num.malloc,
Expand All @@ -379,7 +399,7 @@ JL_DLLEXPORT void *jl_gc_counted_calloc(size_t nm, size_t sz)
jl_task_t *ct = jl_current_task;
if (pgcstack && ct->world_age) {
jl_ptls_t ptls = ct->ptls;
maybe_collect(ptls);
malloc_maybe_collect(ptls, sz);
jl_atomic_store_relaxed(&ptls->gc_num.allocd,
jl_atomic_load_relaxed(&ptls->gc_num.allocd) + nm*sz);
jl_atomic_store_relaxed(&ptls->gc_num.malloc,
Expand Down Expand Up @@ -411,7 +431,7 @@ JL_DLLEXPORT void *jl_gc_counted_realloc_with_old_size(void *p, size_t old, size
jl_task_t *ct = jl_current_task;
if (pgcstack && ct->world_age) {
jl_ptls_t ptls = ct->ptls;
maybe_collect(ptls);
malloc_maybe_collect(ptls, sz);
if (sz < old)
jl_atomic_store_relaxed(&ptls->gc_num.freed,
jl_atomic_load_relaxed(&ptls->gc_num.freed) + (old - sz));
Expand Down