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Change the heuristics to use heap size instead of collected memory #50909

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Change the heuristics to use heap size instead of collected memory #50909

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dd5a826
Change the heuristics to use heap size instead of collected memory
gbaraldi Aug 14, 2023
3145d98
Merge branch 'master' into gb/gc-other-impl
gbaraldi Aug 15, 2023
bca08e2
Merge branch 'master' into gb/gc-other-impl
gbaraldi Sep 12, 2023
89f3578
Make the pacer more like the V8 implementation
gbaraldi Sep 12, 2023
6b66a1a
Reduce tuning_factor
gbaraldi Sep 18, 2023
b19f2e6
Make the GC less greedy
gbaraldi Sep 20, 2023
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32 changes: 14 additions & 18 deletions src/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -691,11 +691,10 @@ static const size_t default_collect_interval = 3200 * 1024 * sizeof(void*);
static memsize_t max_total_memory = (memsize_t) MAX32HEAP;
#endif
// heuristic stuff for https://dl.acm.org/doi/10.1145/3563323
static uint64_t old_pause_time = 0;
static uint64_t old_mut_time = 0;
static uint64_t pause_time_avg = 0;
static uint64_t mut_time_avg = 0;
static uint64_t old_heap_size = 0;
static uint64_t old_alloc_diff = 0;
static uint64_t old_freed_diff = 0;
static uint64_t alloc_diff_avg = 0;
static uint64_t gc_end_time = 0;
static int thrash_counter = 0;
static int thrashing = 0;
Expand Down Expand Up @@ -3317,29 +3316,26 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)
size_t heap_size = jl_atomic_load_relaxed(&gc_heap_stats.heap_size);
double target_allocs = 0.0;
double min_interval = default_collect_interval;
double tuning_factor = 3e-9;
if (collection == JL_GC_AUTO) {
uint64_t alloc_diff = before_free_heap_size - old_heap_size;
uint64_t freed_diff = before_free_heap_size - heap_size;
double alloc_smooth_factor = 0.95;
double collect_smooth_factor = 0.5;
double tuning_factor = 0.03;
double alloc_mem = jl_gc_smooth(old_alloc_diff, alloc_diff, alloc_smooth_factor);
double alloc_time = jl_gc_smooth(old_mut_time, mutator_time + sweep_time, alloc_smooth_factor); // Charge sweeping to the mutator
double gc_mem = jl_gc_smooth(old_freed_diff, freed_diff, collect_smooth_factor);
double gc_time = jl_gc_smooth(old_pause_time, pause - sweep_time, collect_smooth_factor);
old_alloc_diff = alloc_diff;
old_mut_time = mutator_time;
old_freed_diff = freed_diff;
old_pause_time = pause;
double alloc_mem = jl_gc_smooth(alloc_diff_avg, alloc_diff, alloc_smooth_factor);
double alloc_time = jl_gc_smooth(mut_time_avg, mutator_time + sweep_time, alloc_smooth_factor); // Charge sweeping to the mutator
double gc_time = jl_gc_smooth(pause_time_avg, pause - sweep_time, collect_smooth_factor);
alloc_diff_avg = alloc_mem;
mut_time_avg = alloc_time;
pause_time_avg = pause;
old_heap_size = heap_size; // TODO: Update these values dynamically instead of just during the GC
if (gc_time > alloc_time * 95 && !(thrash_counter < 4))
thrash_counter += 1;
else if (thrash_counter > 0)
thrash_counter -= 1;
if (alloc_mem != 0 && alloc_time != 0 && gc_mem != 0 && gc_time != 0 ) {
if (alloc_mem != 0 && alloc_time != 0 && heap_size != 0 && gc_time != 0 ) {
double alloc_rate = alloc_mem/alloc_time;
double gc_rate = gc_mem/gc_time;
target_allocs = sqrt(((double)heap_size/min_interval * alloc_rate)/(gc_rate * tuning_factor)); // work on multiples of min interval
double gc_rate = heap_size/gc_time;
target_allocs = sqrt((double)heap_size * alloc_rate/gc_rate / tuning_factor); // work on multiples of min interval
}
}
if (thrashing == 0 && thrash_counter >= 3)
Expand All @@ -3349,7 +3345,7 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)

int bad_result = (target_allocs*min_interval + heap_size) > 2 * jl_atomic_load_relaxed(&gc_heap_stats.heap_target); // Don't follow through on a bad decision
if (target_allocs == 0.0 || thrashing || bad_result) // If we are thrashing go back to default
target_allocs = 2*sqrt((double)heap_size/min_interval);
target_allocs = sqrt((double)heap_size / tuning_factor);
uint64_t target_heap = (uint64_t)target_allocs*min_interval + heap_size;
if (target_heap > max_total_memory && !thrashing) // Allow it to go over if we are thrashing if we die we die
target_heap = max_total_memory;
Expand Down
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