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avoid over-large buffer for tail calls

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Applying to a large number of arguments once causes the run-time
system to maintain a too-large buffer for managing tail calls in
the future. Decay the buffer size as it is reallocated.
This commit is contained in:
Matthew Flatt 2014-07-11 07:27:36 +01:00
parent 4aa61744c6
commit 94bd5369b5
5 changed files with 29 additions and 30 deletions
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5
racket/src/racket/src/error.c
View File

@ -1362,10 +1362,7 @@ void scheme_wrong_count_m(const char *name, int minc, int maxc,
if (argv == p->tail_buffer) {
/* See calls in scheme_do_eval: */
GC_CAN_IGNORE Scheme_Object **tb;
p->tail_buffer = NULL; /* so args aren't zeroed */
tb = MALLOC_N(Scheme_Object *, p->tail_buffer_size);
p->tail_buffer = tb;
scheme_realloc_tail_buffer(p);
}
/* minc = 1 -> name is really a case-lambda or native proc */

7
racket/src/racket/src/eval.c
View File

@ -1351,12 +1351,7 @@ static void unbound_global(Scheme_Object *obj)
static void make_tail_buffer_safe()
{
Scheme_Thread *p = scheme_current_thread;
GC_CAN_IGNORE Scheme_Object **tb;
p->tail_buffer = NULL; /* so args aren't zeroed */
tb = MALLOC_N(Scheme_Object *, p->tail_buffer_size);
p->tail_buffer = tb;
scheme_realloc_tail_buffer(scheme_current_thread);
}
static Scheme_Object **evacuate_runstack(int num_rands, Scheme_Object **rands, Scheme_Object **runstack)

25
racket/src/racket/src/fun.c
View File

@ -1066,12 +1066,8 @@ void scheme_really_create_overflow(void *stack_base)
p->values_buffer = NULL;
} else if (reply == SCHEME_TAIL_CALL_WAITING) {
p = scheme_current_thread;
if (p->ku.apply.tail_rands == p->tail_buffer) {
GC_CAN_IGNORE Scheme_Object **tb;
p->tail_buffer = NULL; /* so args aren't zeroed */
tb = MALLOC_N(Scheme_Object *, p->tail_buffer_size);
p->tail_buffer = tb;
}
if (p->ku.apply.tail_rands == p->tail_buffer)
scheme_realloc_tail_buffer(p);
}
}
@ -1366,12 +1362,8 @@ force_values(Scheme_Object *obj, int multi_ok)
GC_CAN_IGNORE Scheme_Object **rands;
/* Watch out for use of tail buffer: */
if (p->ku.apply.tail_rands == p->tail_buffer) {
GC_CAN_IGNORE Scheme_Object **tb;
p->tail_buffer = NULL; /* so args aren't zeroed */
tb = MALLOC_N(Scheme_Object *, p->tail_buffer_size);
p->tail_buffer = tb;
}
if (p->ku.apply.tail_rands == p->tail_buffer)
scheme_realloc_tail_buffer(p);
rator = p->ku.apply.tail_rator;
rands = p->ku.apply.tail_rands;
@ -1620,12 +1612,11 @@ scheme_tail_apply (Scheme_Object *rator, int num_rands, Scheme_Object **rands)
if (num_rands) {
Scheme_Object **a;
if (num_rands > p->tail_buffer_size) {
Scheme_Object **tb;
tb = MALLOC_N(Scheme_Object *, num_rands);
p->tail_buffer = tb;
a = MALLOC_N(Scheme_Object *, num_rands);
p->tail_buffer = a;
p->tail_buffer_size = num_rands;
}
a = p->tail_buffer;
} else
a = p->tail_buffer;
p->ku.apply.tail_rands = a;
for (i = num_rands; i--; ) {
a[i] = rands[i];

2
racket/src/racket/src/schpriv.h
View File

@ -665,6 +665,8 @@ void scheme_clear_thread_sync(Scheme_Thread *p);
void scheme_zero_unneeded_rands(Scheme_Thread *p);
void scheme_realloc_tail_buffer(Scheme_Thread *p);
int scheme_can_break(Scheme_Thread *p);
void scheme_thread_wait(Scheme_Object *thread);

20
racket/src/racket/src/thread.c
View File

@ -2505,7 +2505,21 @@ Scheme_Thread *scheme_make_thread(void *stack_base)
return make_thread(NULL, NULL, NULL, NULL, stack_base);
}
static void scheme_check_tail_buffer_size(Scheme_Thread *p)
void scheme_realloc_tail_buffer(Scheme_Thread *p)
{
GC_CAN_IGNORE Scheme_Object **tb;
p->tail_buffer = NULL; /* so args aren't zeroed */
/* Decay cached size back toward the initial size: */
if (p->tail_buffer_size > (buffer_init_size << 1))
p->tail_buffer_size = p->tail_buffer_size >> 1;
tb = MALLOC_N(Scheme_Object *, p->tail_buffer_size);
p->tail_buffer = tb;
}
static void check_tail_buffer_size(Scheme_Thread *p)
{
if (p->tail_buffer_size < buffer_init_size) {
Scheme_Object **tb;
@ -2523,7 +2537,7 @@ void scheme_set_tail_buffer_size(int s)
buffer_init_size = s;
for (p = scheme_first_thread; p; p = p->next) {
scheme_check_tail_buffer_size(p);
check_tail_buffer_size(p);
}
}
}
@ -5412,7 +5426,7 @@ void scheme_weak_resume_thread(Scheme_Thread *r)
r->next->prev = r;
r->ran_some = 1;
schedule_in_set((Scheme_Object *)r, r->t_set_parent);
scheme_check_tail_buffer_size(r);
check_tail_buffer_size(r);
}
}
}