From patchwork Tue Oct 10 00:09:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 13414696 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9390FE95A9C for ; Tue, 10 Oct 2023 00:10:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 277868D009E; Mon, 9 Oct 2023 20:10:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 230D68D0089; Mon, 9 Oct 2023 20:10:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0839A8D009E; Mon, 9 Oct 2023 20:10:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id E56328D0089 for ; Mon, 9 Oct 2023 20:10:06 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B8EDC12044D for ; Tue, 10 Oct 2023 00:10:06 +0000 (UTC) X-FDA: 81327619212.30.FD7F94F Received: from out-193.mta0.migadu.com (out-193.mta0.migadu.com [91.218.175.193]) by imf19.hostedemail.com (Postfix) with ESMTP id 1FBD11A0021 for ; Tue, 10 Oct 2023 00:10:04 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=vYGiTYSo; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf19.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.218.175.193 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1696896605; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UB8UCsgBBNwm/lYUhug39JXjgrJB25jOFlVEA0SwZ1w=; b=1JqnYqNyXV3/MeTi5CfTz8ER7RI7TKY1mgTVFlNdNkpd4HI5I+3zx0x7CjM2e8kPoU63iR dpo6amkKnSDUj6N6A2KOxbkBJpVuBRQUPj5fMGTS78Rvz/bzmPffzuXtOCxM+v0upn3/iF 5cF2t4yVjz7U+iHTn8qPcJXO6PFfTs4= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=vYGiTYSo; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf19.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.218.175.193 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1696896605; a=rsa-sha256; cv=none; b=33MnDCpgfI9zOotGd5GGKe5whylu6J55Vxs6PRO/URTMmpbyQHJJbdRWAU0w+uje/px38D I2WDmLleXUt0iTfseZmcNEP1Pq4MSkDCuK94fq7Yg6Lk0i+hgeMWvY4x3aS0FYvUkF2aYR Ii6M8J7o3tTcKNFDgyEvh+B9I7HWHVo= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1696896601; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UB8UCsgBBNwm/lYUhug39JXjgrJB25jOFlVEA0SwZ1w=; b=vYGiTYSof5OwIfp3SCsmVVAqIIOHV/2QRu9KSEpIse6pPitUQLPoDY3+768geHIe1OotqT gQVtl8qNLJ/m8/vVb6QjGtwGNF5Ng1ivDTPPJOXsC152HcMV8t2pO85z3+N7HypmzHOCBd PAkUbeSbCfQEs0F1f4lfujM5IDfCuz4= From: Roman Gushchin To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Dennis Zhou , Andrew Morton , David Rientjes , Vlastimil Babka , Naresh Kamboju , Roman Gushchin Subject: [PATCH v2 2/5] mm: kmem: add direct objcg pointer to task_struct Date: Mon, 9 Oct 2023 17:09:26 -0700 Message-ID: <20231010000929.450702-3-roman.gushchin@linux.dev> In-Reply-To: <20231010000929.450702-1-roman.gushchin@linux.dev> References: <20231010000929.450702-1-roman.gushchin@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 1FBD11A0021 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: sghkfaompwmmidaia8yqpxb6pht5hkdx X-HE-Tag: 1696896604-2488 X-HE-Meta: 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 YXMkno6E sarChOJjRqTISzFXoE7BpB2zEkrPaPWDAdELEWCx62ns0fcbgFa9E7L+Okextj6Xij/sJmHOwszEY1CmbPCqljaNGydPXgXC9H10ENuCn6cSsRjzkAqhxAMyBV7/bAKGsOE86bMXIstNom4yUShGy9PuwXGs4txwBVjc010hmoTElTv3VnyruxpZakg== 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: To charge a freshly allocated kernel object to a memory cgroup, the kernel needs to obtain an objcg pointer. Currently it does it indirectly by obtaining the memcg pointer first and then calling to __get_obj_cgroup_from_memcg(). Usually tasks spend their entire life belonging to the same object cgroup. So it makes sense to save the objcg pointer on task_struct directly, so it can be obtained faster. It requires some work on fork, exit and cgroup migrate paths, but these paths are way colder. To avoid any costly synchronization the following rules are applied: 1) A task sets it's objcg pointer itself. 2) If a task is being migrated to another cgroup, the least significant bit of the objcg pointer is set atomically. 3) On the allocation path the objcg pointer is obtained locklessly using the READ_ONCE() macro and the least significant bit is checked. If it's set, the following procedure is used to update it locklessly: - task->objcg is zeroed using cmpxcg - new objcg pointer is obtained - task->objcg is updated using try_cmpxchg - operation is repeated if try_cmpxcg fails It guarantees that no updates will be lost if task migration is racing against objcg pointer update. It also allows to keep both read and write paths fully lockless. Because the task is keeping a reference to the objcg, it can't go away while the task is alive. This commit doesn't change the way the remote memcg charging works. Signed-off-by: Roman Gushchin (Cruise) Acked-by: Johannes Weiner --- include/linux/sched.h | 4 ++ mm/memcontrol.c | 130 +++++++++++++++++++++++++++++++++++++++--- 2 files changed, 125 insertions(+), 9 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 77f01ac385f7..60de42715b56 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1443,6 +1443,10 @@ struct task_struct { struct mem_cgroup *active_memcg; #endif +#ifdef CONFIG_MEMCG_KMEM + struct obj_cgroup *objcg; +#endif + #ifdef CONFIG_BLK_CGROUP struct gendisk *throttle_disk; #endif diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 16ac2a5838fb..a2efeea43058 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -249,6 +249,8 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr) return container_of(vmpr, struct mem_cgroup, vmpressure); } +#define CURRENT_OBJCG_UPDATE_FLAG 0x1UL + #ifdef CONFIG_MEMCG_KMEM static DEFINE_SPINLOCK(objcg_lock); @@ -3001,6 +3003,50 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg) return objcg; } +static struct obj_cgroup *current_objcg_update(void) +{ + struct mem_cgroup *memcg; + struct obj_cgroup *old, *objcg = NULL; + + do { + /* Atomically drop the update bit. */ + old = xchg(¤t->objcg, NULL); + if (old) { + old = (struct obj_cgroup *) + ((unsigned long)old & ~CURRENT_OBJCG_UPDATE_FLAG); + if (old) + obj_cgroup_put(old); + + old = NULL; + } + + /* Obtain the new objcg pointer. */ + rcu_read_lock(); + memcg = mem_cgroup_from_task(current); + /* + * The current task can be asynchronously moved to another + * memcg and the previous memcg can be offlined. So let's + * get the memcg pointer and try get a reference to objcg + * under a rcu read lock. + */ + for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) { + objcg = rcu_dereference(memcg->objcg); + if (likely(objcg && obj_cgroup_tryget(objcg))) + break; + objcg = NULL; + } + rcu_read_unlock(); + + /* + * Try set up a new objcg pointer atomically. If it + * fails, it means the update flag was set concurrently, so + * the whole procedure should be repeated. + */ + } while (!try_cmpxchg(¤t->objcg, &old, objcg)); + + return objcg; +} + __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) { struct mem_cgroup *memcg; @@ -3008,19 +3054,26 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) if (in_task()) { memcg = current->active_memcg; + if (unlikely(memcg)) + goto from_memcg; - /* Memcg to charge can't be determined. */ - if (likely(!memcg) && (!current->mm || (current->flags & PF_KTHREAD))) - return NULL; + objcg = READ_ONCE(current->objcg); + if (unlikely((unsigned long)objcg & CURRENT_OBJCG_UPDATE_FLAG)) + objcg = current_objcg_update(); + + if (objcg) { + obj_cgroup_get(objcg); + return objcg; + } } else { memcg = this_cpu_read(int_active_memcg); - if (likely(!memcg)) - return NULL; + if (unlikely(memcg)) + goto from_memcg; } + return NULL; +from_memcg: rcu_read_lock(); - if (!memcg) - memcg = mem_cgroup_from_task(current); objcg = __get_obj_cgroup_from_memcg(memcg); rcu_read_unlock(); return objcg; @@ -6345,6 +6398,7 @@ static void mem_cgroup_move_task(void) mem_cgroup_clear_mc(); } } + #else /* !CONFIG_MMU */ static int mem_cgroup_can_attach(struct cgroup_taskset *tset) { @@ -6358,8 +6412,39 @@ static void mem_cgroup_move_task(void) } #endif +#ifdef CONFIG_MEMCG_KMEM +static void mem_cgroup_fork(struct task_struct *task) +{ + /* + * Set the update flag to cause task->objcg to be initialized lazily + * on the first allocation. It can be done without any synchronization + * because it's always performed on the current task, so does + * current_objcg_update(). + */ + task->objcg = (struct obj_cgroup *)CURRENT_OBJCG_UPDATE_FLAG; +} + +static void mem_cgroup_exit(struct task_struct *task) +{ + struct obj_cgroup *objcg = task->objcg; + + objcg = (struct obj_cgroup *) + ((unsigned long)objcg & ~CURRENT_OBJCG_UPDATE_FLAG); + if (objcg) + obj_cgroup_put(objcg); + + /* + * Some kernel allocations can happen after this point, + * but let's ignore them. It can be done without any synchronization + * because it's always performed on the current task, so does + * current_objcg_update(). + */ + task->objcg = NULL; +} +#endif + #ifdef CONFIG_LRU_GEN -static void mem_cgroup_attach(struct cgroup_taskset *tset) +static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset) { struct task_struct *task; struct cgroup_subsys_state *css; @@ -6377,10 +6462,31 @@ static void mem_cgroup_attach(struct cgroup_taskset *tset) task_unlock(task); } #else +static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset) {} +#endif /* CONFIG_LRU_GEN */ + +#ifdef CONFIG_MEMCG_KMEM +static void mem_cgroup_kmem_attach(struct cgroup_taskset *tset) +{ + struct task_struct *task; + struct cgroup_subsys_state *css; + + cgroup_taskset_for_each(task, css, tset) { + /* atomically set the update bit */ + set_bit(0, (unsigned long *)¤t->objcg); + } +} +#else +static void mem_cgroup_kmem_attach(struct cgroup_taskset *tset) {} +#endif /* CONFIG_MEMCG_KMEM */ + +#if defined(CONFIG_LRU_GEN) || defined(CONFIG_MEMCG_KMEM) static void mem_cgroup_attach(struct cgroup_taskset *tset) { + mem_cgroup_lru_gen_attach(tset); + mem_cgroup_kmem_attach(tset); } -#endif /* CONFIG_LRU_GEN */ +#endif static int seq_puts_memcg_tunable(struct seq_file *m, unsigned long value) { @@ -6824,9 +6930,15 @@ struct cgroup_subsys memory_cgrp_subsys = { .css_reset = mem_cgroup_css_reset, .css_rstat_flush = mem_cgroup_css_rstat_flush, .can_attach = mem_cgroup_can_attach, +#if defined(CONFIG_LRU_GEN) || defined(CONFIG_MEMCG_KMEM) .attach = mem_cgroup_attach, +#endif .cancel_attach = mem_cgroup_cancel_attach, .post_attach = mem_cgroup_move_task, +#ifdef CONFIG_MEMCG_KMEM + .fork = mem_cgroup_fork, + .exit = mem_cgroup_exit, +#endif .dfl_cftypes = memory_files, .legacy_cftypes = mem_cgroup_legacy_files, .early_init = 0,