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Tune GC heuristics for big remsets.
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Take the number of pointers transgressing the generational frontier
into account when deciding wether to do a young or an old gen
collection. Helps #10428. Didn't run the bench suite yet.
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@carnaval @yuyichao
carnaval authored and yuyichao committed Aug 15, 2015
1 parent 181c19f commit 8edc1dc
Showing 1 changed file with 26 additions and 7 deletions.
33 changes: 26 additions & 7 deletions src/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@ static GC_Num gc_num = {0,0,0,0,0,0,0,0,0,0,0,0,0};
#define total_gc_time gc_num.total_time
#define total_allocd_bytes gc_num.total_allocd
#define allocd_bytes_since_sweep gc_num.since_sweep
static size_t last_long_collect_interval;

typedef struct _buff_t {
union {
Expand Down Expand Up @@ -209,6 +210,8 @@ HEAP_DECL bigval_t *big_objects;
// variables for tracking "remembered set"
HEAP_DECL arraylist_t rem_bindings;
HEAP_DECL arraylist_t _remset[2]; // contains jl_value_t*
// lower bound of the number of pointers inside remembered values
static int remset_nptr;
HEAP_DECL arraylist_t *remset;
HEAP_DECL arraylist_t *last_remset;

Expand Down Expand Up @@ -459,8 +462,8 @@ static htable_t obj_counts[3];
static htable_t obj_sizes[3];
#endif

DLLEXPORT size_t jl_gc_total_freed_bytes=0;
#ifdef GC_FINAL_STATS
static size_t total_freed_bytes = 0;
static uint64_t max_pause = 0;
static uint64_t total_sweep_time = 0;
static uint64_t total_mark_time = 0;
Expand Down Expand Up @@ -1437,6 +1440,7 @@ static void reset_remset(void)
remset = last_remset;
last_remset = tmp;
remset->len = 0;
remset_nptr = 0;
END
}

Expand All @@ -1447,6 +1451,7 @@ DLLEXPORT void jl_gc_queue_root(jl_value_t *ptr)
assert(gc_bits(o) != GC_QUEUED);
gc_bits(o) = GC_QUEUED;
arraylist_push(remset, ptr);
remset_nptr++; // conservative
END
}

Expand Down Expand Up @@ -1611,7 +1616,7 @@ static int push_root(jl_value_t *v, int d, int bits)
{
assert(v != NULL);
jl_value_t *vt = (jl_value_t*)gc_typeof(v);
int refyoung = 0;
int refyoung = 0, nptr = 0;

if (vt == (jl_value_t*)jl_weakref_type) {
bits = gc_setmark(v, sizeof(jl_weakref_t), GC_MARKED_NOESC);
Expand All @@ -1637,6 +1642,7 @@ static int push_root(jl_value_t *v, int d, int bits)
size_t l = jl_svec_len(v);
MARK(v, bits = gc_setmark(v, l*sizeof(void*) + sizeof(jl_svec_t), GC_MARKED_NOESC));
jl_value_t **data = ((jl_svec_t*)v)->data;
nptr += l;
for(size_t i=0; i < l; i++) {
jl_value_t *elt = data[i];
if (elt != NULL) {
Expand Down Expand Up @@ -1694,6 +1700,7 @@ static int push_root(jl_value_t *v, int d, int bits)
goto queue_the_root;
}
else {
nptr += l;
void *data = a->data;
for(size_t i=0; i < l; i++) {
jl_value_t *elt = ((jl_value_t**)data)[i];
Expand All @@ -1708,10 +1715,12 @@ static int push_root(jl_value_t *v, int d, int bits)
}
}
else if (vt == (jl_value_t*)jl_module_type) {
// should increase nptr here
MARK(v, bits = gc_setmark(v, sizeof(jl_module_t), GC_MARKED_NOESC));
refyoung |= gc_mark_module((jl_module_t*)v, d);
}
else if (vt == (jl_value_t*)jl_task_type) {
// ditto nptr
MARK(v, bits = gc_setmark(v, sizeof(jl_task_t), GC_MARKED_NOESC));
gc_mark_task((jl_task_t*)v, d);
// tasks should always be remarked since we do not trigger the write barrier
Expand All @@ -1738,6 +1747,7 @@ static int push_root(jl_value_t *v, int d, int bits)
jl_fielddesc_t* fields = dt->fields;
for(int i=0; i < nf; i++) {
if (fields[i].isptr) {
nptr++;
jl_value_t **slot = (jl_value_t**)((char*)v + fields[i].offset);
jl_value_t *fld = *slot;
if (fld) {
Expand All @@ -1761,6 +1771,7 @@ static int push_root(jl_value_t *v, int d, int bits)
if (verifying) return bits;
#endif
if ((bits == GC_MARKED) && (refyoung == GC_MARKED_NOESC)) {
remset_nptr += nptr;
FOR_CURRENT_HEAP
// v is an old object referencing young objects
arraylist_push(remset, v);
Expand Down Expand Up @@ -2051,7 +2062,9 @@ void jl_gc_collect(int full)
uint64_t mark_pause = jl_hrtime() - t0;
#endif
#ifdef GC_TIME
jl_printf(JL_STDOUT, "GC mark pause %.2f ms | scanned %ld kB = %ld + %ld | stack %d -> %d (wb %d) | remset %d %d\n", NS2MS(mark_pause), (scanned_bytes + perm_scanned_bytes)/1024, scanned_bytes/1024, perm_scanned_bytes/1024, saved_mark_sp, mark_sp, wb_activations, last_remset->len, allocd_bytes/1024);
FOR_EACH_HEAP
jl_printf(JL_STDOUT, "GC mark pause %.2f ms | scanned %ld kB = %ld + %ld | stack %d -> %d (wb %d) | remset %d %d\n", NS2MS(mark_pause), (scanned_bytes + perm_scanned_bytes)/1024, scanned_bytes/1024, perm_scanned_bytes/1024, saved_mark_sp, mark_sp, wb_activations, last_remset->len, remset_nptr);
END
saved_mark_sp = mark_sp;
#endif
#ifdef GC_FINAL_STATS
Expand Down Expand Up @@ -2101,17 +2114,21 @@ void jl_gc_collect(int full)
promoted_bytes += perm_scanned_bytes - last_perm_scanned_bytes;
// 5. next collection decision
int not_freed_enough = estimate_freed < (7*(actual_allocd/10));
if ((full || ((not_freed_enough || promoted_bytes >= collect_interval) && (promoted_bytes >= default_collect_interval || prev_sweep_mask == GC_MARKED))) && n_pause > 1) {
int large_frontier = remset_nptr*sizeof(void*) >= default_collect_interval; // many pointers in the intergen frontier => "quick" mark is not quick
if ((full || large_frontier || ((not_freed_enough || promoted_bytes >= collect_interval) && (promoted_bytes >= default_collect_interval || prev_sweep_mask == GC_MARKED))) && n_pause > 1) {
if (prev_sweep_mask != GC_MARKED || full) {
if (full) recollect = 1; // TODO enable this?
}
if (not_freed_enough) {
if (large_frontier)
collect_interval = last_long_collect_interval;
if (not_freed_enough || large_frontier) {
if (collect_interval < default_collect_interval)
collect_interval = default_collect_interval;
else if (collect_interval <= 2*(max_collect_interval/5)) {
collect_interval = 5*(collect_interval/2);
}
}
last_long_collect_interval = collect_interval;
sweep_mask = GC_MARKED;
promoted_bytes = 0;
quick_count = 0;
Expand Down Expand Up @@ -2167,6 +2184,7 @@ void jl_gc_collect(int full)
inc_count = 0;
live_bytes += -freed_bytes + allocd_bytes_since_sweep;
allocd_bytes_since_sweep = 0;
jl_gc_total_freed_bytes += freed_bytes;
freed_bytes = 0;

#if defined(GC_FINAL_STATS) || defined(GC_TIME)
Expand Down Expand Up @@ -2335,8 +2353,8 @@ void jl_print_gc_stats(JL_STREAM *s)
struct mallinfo mi = mallinfo();
jl_printf(s, "malloc size\t%d MB\n", mi.uordblks/1024/1024);
jl_printf(s, "max page alloc\t%ld MB\n", max_pg_count*GC_PAGE_SZ/1024/1024);
jl_printf(s, "total freed\t%" PRIuPTR " b\n", total_freed_bytes);
jl_printf(s, "free rate\t%.1f MB/sec\n", (total_freed_bytes/gct)/1024/1024);
jl_printf(s, "total freed\t%" PRIuPTR " b\n", jl_gc_total_freed_bytes);
jl_printf(s, "free rate\t%.1f MB/sec\n", (jl_gc_total_freed_bytes/gct)/1024/1024);
}
#endif

Expand Down Expand Up @@ -2377,6 +2395,7 @@ void jl_gc_init(void)
arraylist_new(&to_finalize, 0);

collect_interval = default_collect_interval;
last_long_collect_interval = default_collect_interval;
allocd_bytes = -default_collect_interval;

#ifdef GC_VERIFY
Expand Down

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