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reduce double major GCs

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When a major GC triggers finalization, another major
GC is scheduled immediately on the grounds that the
finalizer may release other values. That was important
at once time, but the finalization and weak-reference
implementation has improved to the point where the
extra ful GC no longer seems necessary or useful.
This commit is contained in:
Matthew Flatt 2015-12-19 11:35:41 -07:00
parent 513849c1e3
commit 3a99a19c56
2 changed files with 10 additions and 24 deletions
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32
racket/src/racket/gc2/newgc.c
View File

@ -6086,11 +6086,6 @@ static int mark_and_finalize_all_incremental(NewGC *gc, int no_full TIME_FORMAL_
return more_to_do;
}
/* Full GCs trigger finalization. Finalization releases data
in the old generation. So one more full GC is needed to
really clean up. The full_needed_for_finalization flag triggers
the second full GC. */
static void garbage_collect(NewGC *gc, int force_full, int no_full, int switching_master, Log_Master_Info *lmi)
{
uintptr_t old_mem_use;
@ -6130,7 +6125,7 @@ static void garbage_collect(NewGC *gc, int force_full, int no_full, int switchin
&& !gc->started_incremental)
/* Finalization triggers an extra full in case it releases
a lot of additional memory: */
|| (gc->full_needed_for_finalization
|| (gc->full_needed_again
&& !gc->incremental_requested
&& !gc->started_incremental)
/* In incremental mode, GC earlier if we've done everything
@ -6140,13 +6135,16 @@ static void garbage_collect(NewGC *gc, int force_full, int no_full, int switchin
if (gc->gc_full && no_full)
return;
/* Switch from incremental to not, schedule another
full GC for next time: */
next_gc_full = (gc->gc_full
&& gc->started_incremental
&& !gc->incremental_requested
&& !always_collect_incremental_on_minor
&& !gc->full_needed_for_finalization);
&& !gc->full_needed_again);
if (gc->full_needed_for_finalization && gc->gc_full)
gc->full_needed_for_finalization= 0;
if (gc->full_needed_again && gc->gc_full)
gc->full_needed_again = 0;
#ifdef GC_DEBUG_PAGES
if (gc->gc_full == 1) {
@ -6454,17 +6452,6 @@ static void garbage_collect(NewGC *gc, int force_full, int no_full, int switchin
if (gc->gc_full)
merge_run_queues(gc);
if (!gc->run_queue) {
if (had_started_incremental) {
/* Keep next_gc_full, if it's set, because that means incremental
mode wasn't requested recently, even through we're wrapping up
an incremental GC; another major GC is likely to reclaim more
memory, reduce fragentation, and generally improve heap
health */
} else
next_gc_full = 0;
}
/* Run any queued finalizers, EXCEPT in the case where this
collection was triggered during the execution of a finalizer.
Without the exception, finalization effectively becomes
@ -6500,13 +6487,12 @@ static void garbage_collect(NewGC *gc, int force_full, int no_full, int switchin
gc->park[1] = gc->park_fsave[1];
gc->park_fsave[0] = NULL;
gc->park_fsave[1] = NULL;
} else
next_gc_full = 0;
}
DUMP_HEAP(); CLOSE_DEBUG_FILE();
if (next_gc_full)
gc->full_needed_for_finalization = 1;
gc->full_needed_again = 1;
#ifdef MZ_USE_PLACES
if (postmaster_and_place_gc(gc)) {

2
racket/src/racket/gc2/newgc.h
View File

@ -216,7 +216,7 @@ typedef struct NewGC {
unsigned char finished_incremental :1; /* finished marking and reparing an incremental GC */
unsigned char accounted_incremental :1; /* memory accounting for an incremental GC */
unsigned char in_unsafe_allocation_mode :1;
unsigned char full_needed_for_finalization :1;
unsigned char full_needed_again :1;
unsigned char no_further_modifications :1;
unsigned char gc_full :1; /* a flag saying if this is a full/major collection */
unsigned char had_finished_incremental :1; /* when gc_full, indicates full GC after incremental finished */