On Wed, Feb 28, 2024 at 05:48:53PM +0800, Baoquan He wrote:
> On 01/02/24 at 07:46pm, Uladzislau Rezki (Sony) wrote:
> .....snip...
> > +static void
> > +decay_va_pool_node(struct vmap_node *vn, bool full_decay)
> > +{
> > + struct vmap_area *va, *nva;
> > + struct list_head decay_list;
> > + struct rb_root decay_root;
> > + unsigned long n_decay;
> > + int i;
> > +
> > + decay_root = RB_ROOT;
> > + INIT_LIST_HEAD(&decay_list);
> > +
> > + for (i = 0; i < MAX_VA_SIZE_PAGES; i++) {
> > + struct list_head tmp_list;
> > +
> > + if (list_empty(&vn->pool[i].head))
> > + continue;
> > +
> > + INIT_LIST_HEAD(&tmp_list);
> > +
> > + /* Detach the pool, so no-one can access it. */
> > + spin_lock(&vn->pool_lock);
> > + list_replace_init(&vn->pool[i].head, &tmp_list);
> > + spin_unlock(&vn->pool_lock);
> > +
> > + if (full_decay)
> > + WRITE_ONCE(vn->pool[i].len, 0);
> > +
> > + /* Decay a pool by ~25% out of left objects. */
>
> This isn't true if the pool has less than 4 objects. If there are 3
> objects, n_decay = 0.
>
This is expectable.
> > + n_decay = vn->pool[i].len >> 2;
> > +
> > + list_for_each_entry_safe(va, nva, &tmp_list, list) {
> > + list_del_init(&va->list);
> > + merge_or_add_vmap_area(va, &decay_root, &decay_list);
> > +
> > + if (!full_decay) {
> > + WRITE_ONCE(vn->pool[i].len, vn->pool[i].len - 1);
> > +
> > + if (!--n_decay)
> > + break;
>
> Here, --n_decay will make n_decay 0xffffffffffffffff,
> then all left objects are reclaimed.
Right. Last three objects do not play a big game.
--
Uladzislau Rezki
