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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: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 X-Rspamd-Queue-Id: 4D80E40020 X-Rspam-User: X-Stat-Signature: hbjn3dsjb7s198pi3hqw17zdi5uk8otd X-Rspamd-Server: rspam03 X-HE-Tag: 1709123197-53363 X-HE-Meta: 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 yjN0ZdJ5 abslWOJOufulqBiJfV5hyFJLUfnhRwa5trML6g1rOCsWh69ZTuRmy14Y398dnmtQoaAV0zbg+dSJ+CyvfUaqVzYHMl0q2nbZKeMOUAjM32YBKQMqlAndksbmZ+IZYcwyzkTzao9CRdx2klw4nO0wJD2OQUQMODi7fT5KSovfYbewZep+7YkKTTCunyAFo+vkMNKwcgVxE/O6Pvarw4ZBlHm5W1wIGayu8Uw+ipr5BjfWc31yOxq5gMr8b9A== 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 02/28/24 at 11:39am, Uladzislau Rezki wrote: > 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. See it now, thanks.