project-base/server-skynet-source-3rd-jemalloc
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Improve the fit for aligned allocation.

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We compute the max size required to satisfy an alignment.  However this can be
quite pessimistic, especially with frequent reuse (and combined with state-based
fragmentation).  This commit adds one more fit step specific to aligned
allocations, searching in all potential fit size classes.
This commit is contained in:
Qi Wang 2017-12-21 16:17:45 -08:00 committed by Qi Wang
parent 41790f4fa4
commit ba5992fe9a
1 changed files with 61 additions and 10 deletions
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71
src/extent.c
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@ -363,6 +363,43 @@ extents_remove_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent,
cur_extents_npages - (size >> LG_PAGE), ATOMIC_RELAXED);
}
/*
* Find an extent with size [min_size, max_size) to satisfy the alignment
* requirement. For each size, try only the first extent in the heap.
*/
static extent_t *
extents_fit_alignment(extents_t *extents, size_t min_size, size_t max_size,
size_t alignment) {
pszind_t pind = sz_psz2ind(extent_size_quantize_ceil(min_size));
pszind_t pind_max = sz_psz2ind(extent_size_quantize_ceil(max_size));
for (pszind_t i = (pszind_t)bitmap_ffu(extents->bitmap,
&extents_bitmap_info, (size_t)pind); i < pind_max; i =
(pszind_t)bitmap_ffu(extents->bitmap, &extents_bitmap_info,
(size_t)i+1)) {
assert(i < NPSIZES);
assert(!extent_heap_empty(&extents->heaps[i]));
extent_t *extent = extent_heap_first(&extents->heaps[i]);
uintptr_t base = (uintptr_t)extent_base_get(extent);
size_t candidate_size = extent_size_get(extent);
assert(candidate_size >= min_size);
uintptr_t next_align = ALIGNMENT_CEILING((uintptr_t)base,
PAGE_CEILING(alignment));
if (base > next_align || base + candidate_size <= next_align) {
/* Overflow or not crossing the next alignment. */
continue;
}
size_t leadsize = next_align - base;
if (candidate_size - leadsize >= min_size) {
return extent;
}
}
return NULL;
}
/* Do any-best-fit extent selection, i.e. select any extent that best fits. */
static extent_t *
extents_best_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
@ -424,12 +461,30 @@ extents_first_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
*/
static extent_t *
extents_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
size_t size) {
size_t esize, size_t alignment) {
malloc_mutex_assert_owner(tsdn, &extents->mtx);
return extents->delay_coalesce ? extents_best_fit_locked(tsdn, arena,
extents, size) : extents_first_fit_locked(tsdn, arena, extents,
size);
size_t max_size = esize + PAGE_CEILING(alignment) - PAGE;
/* Beware size_t wrap-around. */
if (max_size < esize) {
return NULL;
}
extent_t *extent = extents->delay_coalesce ?
extents_best_fit_locked(tsdn, arena, extents, max_size) :
extents_first_fit_locked(tsdn, arena, extents, max_size);
if (alignment > PAGE && extent == NULL) {
/*
* max_size guarantees the alignment requirement but is rather
* pessimistic. Next we try to satisfy the aligned allocation
* with sizes in [esize, max_size).
*/
extent = extents_fit_alignment(extents, esize, max_size,
alignment);
}
return extent;
}
static bool
@ -821,11 +876,6 @@ extent_recycle_extract(tsdn_t *tsdn, arena_t *arena,
}
size_t esize = size + pad;
size_t alloc_size = esize + PAGE_CEILING(alignment) - PAGE;
/* Beware size_t wrap-around. */
if (alloc_size < esize) {
return NULL;
}
malloc_mutex_lock(tsdn, &extents->mtx);
extent_hooks_assure_initialized(arena, r_extent_hooks);
extent_t *extent;
@ -847,7 +897,8 @@ extent_recycle_extract(tsdn_t *tsdn, arena_t *arena,
extent_unlock(tsdn, unlock_extent);
}
} else {
extent = extents_fit_locked(tsdn, arena, extents, alloc_size);
extent = extents_fit_locked(tsdn, arena, extents, esize,
alignment);
}
if (extent == NULL) {
malloc_mutex_unlock(tsdn, &extents->mtx);