adjust some gc heuristics (JuliaLang#32556)

- trigger a full collection if live size grows a lot and stays there
- use a larger minor collect interval based on live_bytes

helps JuliaLang#32472 and JuliaLang#28986

src/gc.c

@@ -571,42 +571,14 @@ static int prev_sweep_full = 1;
 // Full collection heuristics
 static int64_t live_bytes = 0;
 static int64_t promoted_bytes = 0;
+static int64_t last_full_live = 0; // live_bytes after last full collection
+static int64_t last_live_bytes = 0; // live_bytes at last collection
+static int64_t grown_heap_age = 0; // # of collects since live_bytes grew and remained
 #ifdef __GLIBC__
 // maxrss at last malloc_trim
 static int64_t last_trim_maxrss = 0;
 #endif
 
-static int64_t last_full_live_ub = 0;
-static int64_t last_full_live_est = 0;
-// upper bound and estimated live object sizes
-// This heuristic should be really unlikely to trigger.
-// However, this should be simple enough to trigger a full collection
-// when it's necessary if other heuristics are messed up.
-// It is also possible to take the total memory available into account
-// if necessary.
-STATIC_INLINE int gc_check_heap_size(int64_t sz_ub, int64_t sz_est)
-{
- if (__unlikely(!last_full_live_ub || last_full_live_ub > sz_ub)) {
- last_full_live_ub = sz_ub;
- }
- else if (__unlikely(last_full_live_ub * 3 / 2 < sz_ub)) {
- return 1;
- }
- if (__unlikely(!last_full_live_est || last_full_live_est > sz_est)) {
- last_full_live_est = sz_est;
- }
- else if (__unlikely(last_full_live_est * 2 < sz_est)) {
- return 1;
- }
- return 0;
-}
-
-STATIC_INLINE void gc_update_heap_size(int64_t sz_ub, int64_t sz_est)
-{
- last_full_live_ub = sz_ub;
- last_full_live_est = sz_est;
-}
-
 static void gc_sync_cache_nolock(jl_ptls_t ptls, jl_gc_mark_cache_t *gc_cache) JL_NOTSAFEPOINT
 {
  const int nbig = gc_cache->nbig_obj;
@@ -2834,20 +2806,25 @@ static int _jl_gc_collect(jl_ptls_t ptls, int full)
  int large_frontier = nptr*sizeof(void*) >= default_collect_interval; // many pointers in the intergen frontier => "quick" mark is not quick
  int sweep_full;
  int recollect = 0;
+ // trigger a full collection if the number of live bytes doubles since the last full
+ // collection and then remains at least that high for a while.
+ if (grown_heap_age == 0) {
+ if (live_bytes > 2 * last_full_live)
+ grown_heap_age = 1;
+ }
+ else if (live_bytes >= last_live_bytes) {
+ grown_heap_age++;
+ }
  if ((full || large_frontier ||
  ((not_freed_enough || promoted_bytes >= gc_num.interval) &&
  (promoted_bytes >= default_collect_interval || prev_sweep_full)) ||
- gc_check_heap_size(live_sz_ub, live_sz_est)) &&
+ grown_heap_age > 1) &&
  gc_num.pause > 1) {
- gc_update_heap_size(live_sz_ub, live_sz_est);
  recollect = full;
  if (large_frontier)
  gc_num.interval = last_long_collect_interval;
  if (not_freed_enough || large_frontier) {
- if (gc_num.interval < default_collect_interval) {
- gc_num.interval = default_collect_interval;
- }
- else if (gc_num.interval <= 2*(max_collect_interval/5)) {
+ if (gc_num.interval <= 2*(max_collect_interval/5)) {
  gc_num.interval = 5 * (gc_num.interval / 2);
  }
  }
@@ -2856,7 +2833,12 @@ static int _jl_gc_collect(jl_ptls_t ptls, int full)
  promoted_bytes = 0;
  }
  else {
- gc_num.interval = default_collect_interval / 2;
+ // reset interval to default, or at least half of live_bytes
+ int64_t half = live_bytes/2;
+ if (default_collect_interval < half && half <= max_collect_interval)
+ gc_num.interval = half;
+ else
+ gc_num.interval = default_collect_interval;
  sweep_full = gc_sweep_always_full;
  }
  if (sweep_full)
@@ -2910,9 +2892,14 @@ static int _jl_gc_collect(jl_ptls_t ptls, int full)
  gc_time_sweep_pause(gc_end_t, actual_allocd, live_bytes,
  estimate_freed, sweep_full);
  gc_num.full_sweep += sweep_full;
- prev_sweep_full = sweep_full;
  gc_num.allocd = -(int64_t)gc_num.interval;
+ last_live_bytes = live_bytes;
  live_bytes += -gc_num.freed + gc_num.since_sweep;
+ if (prev_sweep_full) {
+ last_full_live = live_bytes;
+ grown_heap_age = 0;
+ }
+ prev_sweep_full = sweep_full;
  gc_num.pause += !recollect;
  gc_num.total_time += pause;
  gc_num.since_sweep = 0;