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Howlett" , Dave Chinner , "Paul E . McKenney" , Joel Fernandes , Oleksiy Avramchenko Subject: Re: [PATCH v3 07/11] mm: vmalloc: Offload free_vmap_area_lock lock Message-ID: References: <20240102184633.748113-1-urezki@gmail.com> <20240102184633.748113-8-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240102184633.748113-8-urezki@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-Stat-Signature: ikrkzsg4e47yme7ynywynji1s3bcmjdt X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: B631B14000F X-Rspam-User: X-HE-Tag: 1709113743-61165 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. > + 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. > + } > + } > + > + /* Attach the pool back if it has been partly decayed. */ > + if (!full_decay && !list_empty(&tmp_list)) { > + spin_lock(&vn->pool_lock); > + list_replace_init(&tmp_list, &vn->pool[i].head); > + spin_unlock(&vn->pool_lock); > + } > + } > + > + reclaim_list_global(&decay_list); > +} ......snip