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Add dead slot map cache

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* libguile/vm.c (find_dead_slot_map, scm_i_vm_mark_stack): Use a little
  cache for dead slot maps.  Helps when marking very deep recursive
  stacks.
This commit is contained in:
Andy Wingo 2014-02-02 11:43:03 +01:00
parent 7dba1c2ff1
commit 407190060b
1 changed files with 36 additions and 2 deletions
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38
libguile/vm.c
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@ -824,6 +824,38 @@ return_unused_stack_to_os (struct scm_vm *vp)
#endif
}
#define DEAD_SLOT_MAP_CACHE_SIZE 32U
struct dead_slot_map_cache_entry
{
scm_t_uint32 *ip;
const scm_t_uint8 *map;
};
struct dead_slot_map_cache
{
struct dead_slot_map_cache_entry entries[DEAD_SLOT_MAP_CACHE_SIZE];
};
static const scm_t_uint8 *
find_dead_slot_map (scm_t_uint32 *ip, struct dead_slot_map_cache *cache)
{
/* The lower two bits should be zero. FIXME: Use a better hash
function; we don't expose scm_raw_hashq currently. */
size_t slot = (((scm_t_uintptr) ip) >> 2) % DEAD_SLOT_MAP_CACHE_SIZE;
const scm_t_uint8 *map;
if (cache->entries[slot].ip == ip)
map = cache->entries[slot].map;
else
{
map = scm_find_dead_slot_map_unlocked (ip);
cache->entries[slot].ip = ip;
cache->entries[slot].map = map;
}
return map;
}
/* Mark the VM stack region between its base and its current top. */
struct GC_ms_entry *
scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry *mark_stack_ptr,
@ -838,6 +870,9 @@ scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry *mark_stack_ptr,
const scm_t_uint8 *dead_slots = NULL;
scm_t_uintptr upper = (scm_t_uintptr) GC_greatest_plausible_heap_addr;
scm_t_uintptr lower = (scm_t_uintptr) GC_least_plausible_heap_addr;
struct dead_slot_map_cache cache;
memset (&cache, 0, sizeof (cache));
for (fp = vp->fp, sp = vp->sp; fp; fp = SCM_FRAME_DYNAMIC_LINK (fp))
{
@ -870,8 +905,7 @@ scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry *mark_stack_ptr,
Note that there may be other reasons to not have a dead slots
map, e.g. if all of the frame's slots below the callee frame
are live. */
dead_slots =
scm_find_dead_slot_map_unlocked (SCM_FRAME_RETURN_ADDRESS (fp));
dead_slots = find_dead_slot_map (SCM_FRAME_RETURN_ADDRESS (fp), &cache);
}
return_unused_stack_to_os (vp);