[Tarantool-patches] [PATCH] do not keep a slab in cache if new allocation does not fit
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Wed Feb 5 00:25:14 MSK 2020
Hi! Thanks for the patch!
On 27/01/2020 20:39, Georgy Kirichenko wrote:
> Do not allocate a new slab if there is a free slab in a region cache.
> If a cached slab is not big enough then free it.
Please, describe the problem you are trying to solve. The
text above just narrates the code.
> Follow up 67d7ab44ab09df3356929e3692a03321b31f3ebb
>
> Fixes #12
Well, the slabs still are not freed in case there was a spike
which allocated lots of slabs, and then only 1-2 are used, and
all allocations fit into the existing slabs.
>
> Issue: https://github.com/tarantool/small/issues/12
> Branch: https://github.com/tarantool/small/tree/g.kirichenko/gh-12-region-cache
>
> diff --git a/small/region.h b/small/region.h
> index d9be176..58481b0 100644
> --- a/small/region.h
> +++ b/small/region.h
> @@ -157,14 +157,20 @@ region_reserve(struct region *region, size_t size)
> if (size <= rslab_unused(slab))
> return (char *) rslab_data(slab) + slab->used;
> /* Try to get a slab from the region cache. */
> - slab = rlist_last_entry(®ion->slabs.slabs,
> - struct rslab,
> - slab.next_in_list);
> - if (slab->used == 0 && size <= rslab_unused(slab)) {
> - /* Move this slab to the head. */
> + while ((slab = rlist_last_entry(®ion->slabs.slabs,
> + struct rslab,
> + slab.next_in_list))->used == 0) {
> slab_list_del(®ion->slabs, &slab->slab, next_in_list);
> - slab_list_add(®ion->slabs, &slab->slab, next_in_list);
> - return (char *) rslab_data(slab);
> + if (size <= rslab_unused(slab)) {
> + /* Move this slab to the head. */
> + slab_list_add(®ion->slabs, &slab->slab, next_in_list);
> + return (char *) rslab_data(slab);
> + }
> + /*
> + * This cached slab could not be used so free it
> + * and try to use the next one.
> + */
> + slab_put(region->cache, (struct slab *)slab);
> }
> }
> return region_reserve_slow(region, size);
>
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