From patchwork Sat Jun 24 03:13:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 13291587 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AEA4EB64DA for ; Sat, 24 Jun 2023 03:14:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229779AbjFXDOL (ORCPT ); Fri, 23 Jun 2023 23:14:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbjFXDOK (ORCPT ); Fri, 23 Jun 2023 23:14:10 -0400 Received: from mail-ot1-x32d.google.com (mail-ot1-x32d.google.com [IPv6:2607:f8b0:4864:20::32d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 65270E47; Fri, 23 Jun 2023 20:14:09 -0700 (PDT) Received: by mail-ot1-x32d.google.com with SMTP id 46e09a7af769-6b711c3ad1fso1189667a34.0; Fri, 23 Jun 2023 20:14:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1687576448; x=1690168448; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=5rMpHCpyAwYur1+foqQGqDjqSKhTON8KzkS42uHp7Vs=; b=CUcGfrhmhl9NtZX7D/yOa94cfvd4Zw53ZvXOnTyfAhAeOB57jlu2hzsPIa+3tB7qGI F99RQiGMR0oEQpNRtdRaxh/azMNpSXFv5F0E9mHfrY/Dj3auFwpjlIQHThGlUDwFNhlJ WK7fYf65apVL6WhXq7DP7wT1aTfd5dof5urV5MQurCQFuOXoC2BGkQC465OvJbpEbTmE MZMKDnvLaJBoGqf2wgAXXcfE6azRuQBKyPRfOz7SnLmkq0VKLvfqpHUUxDMiVbH/z2xL fCo/EiyGiQM2Bval/7d1fbXEQIl6AH0QiZ1am+e1b3P45srsDN7q1FBh7vEiEIRBWm3e l+4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687576448; x=1690168448; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=5rMpHCpyAwYur1+foqQGqDjqSKhTON8KzkS42uHp7Vs=; b=BBAlnWSONq0SS/aZHFVYK0OhhyE74VbTTnVSacSJnmx6RWPWykrJYT2XVNwI9jPHcp x9WxqtpFP2tdNQmvClFtJ/f9l95jThSLS5EbVmvR/sjD1jSaQH2SBA1L60eBwUGBpnJH 9XqJ+pk6xRn/SKQpgI7rZ1QW+HstQtldsi3D1sRqvUAZUBDUrEc9zXZdZJ0dZRCGu6PK 644D01QBClxCBx4z1bMoO89eBdvSZZXkR+Q8k6FM04+9Ls6rG9/nsYX0UvMvixQu2UCZ kn7Vokri4OQ+s9Fp4rWTm+GOIeY7M+dbR7/TX2fg6/22abBXufCvN28HwhOkhCli0zep 68kA== X-Gm-Message-State: AC+VfDxRxc2+vEoIfyx61vVVl6cnb6LCw/Lw+03LXwLicz0RZSWSoTK1 SLa8Qul0KQeGZZGHL2HG4GH0EM3UVsU= X-Google-Smtp-Source: ACHHUZ7HSDtqcXLFJV7RPojw+TX3/T2Q3dBKp2lXq+wxtsx2dl1JPFqiBaHy6zo2cOGLThId3/SQNw== X-Received: by 2002:a05:6358:5118:b0:132:d796:5c6f with SMTP id 24-20020a056358511800b00132d7965c6fmr4648198rwi.20.1687576448468; Fri, 23 Jun 2023 20:14:08 -0700 (PDT) Received: from localhost.localdomain ([2620:10d:c090:400::5:b07c]) by smtp.gmail.com with ESMTPSA id s18-20020a170902b19200b001b3d8ac1b6bsm232231plr.212.2023.06.23.20.14.06 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 23 Jun 2023 20:14:08 -0700 (PDT) From: Alexei Starovoitov To: daniel@iogearbox.net, andrii@kernel.org, void@manifault.com, houtao@huaweicloud.com, paulmck@kernel.org Cc: tj@kernel.org, rcu@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v2 bpf-next 08/13] bpf: Add a hint to allocated objects. Date: Fri, 23 Jun 2023 20:13:28 -0700 Message-Id: <20230624031333.96597-9-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20230624031333.96597-1-alexei.starovoitov@gmail.com> References: <20230624031333.96597-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Alexei Starovoitov To address OOM issue when one cpu is allocating and another cpu is freeing add a target bpf_mem_cache hint to allocated objects and when local cpu free_llist overflows free to that bpf_mem_cache. The hint addresses the OOM while maintaing the same performance for common case when alloc/free are done on the same cpu. Signed-off-by: Alexei Starovoitov --- kernel/bpf/memalloc.c | 46 ++++++++++++++++++++++++++----------------- 1 file changed, 28 insertions(+), 18 deletions(-) diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index d68a854f45ee..692a9a30c1dc 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -99,6 +99,7 @@ struct bpf_mem_cache { int low_watermark, high_watermark, batch; int percpu_size; bool draining; + struct bpf_mem_cache *tgt; /* list of objects to be freed after RCU tasks trace GP */ struct llist_head free_by_rcu_ttrace; @@ -190,18 +191,11 @@ static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node) for (i = 0; i < cnt; i++) { /* - * free_by_rcu_ttrace is only manipulated by irq work refill_work(). - * IRQ works on the same CPU are called sequentially, so it is - * safe to use __llist_del_first() here. If alloc_bulk() is - * invoked by the initial prefill, there will be no running - * refill_work(), so __llist_del_first() is fine as well. - * - * In most cases, objects on free_by_rcu_ttrace are from the same CPU. - * If some objects come from other CPUs, it doesn't incur any - * harm because NUMA_NO_NODE means the preference for current - * numa node and it is not a guarantee. + * For every 'c' llist_del_first(&c->free_by_rcu_ttrace); is + * done only by one CPU == current CPU. Other CPUs might + * llist_add() and llist_del_all() in parallel. */ - obj = __llist_del_first(&c->free_by_rcu_ttrace); + obj = llist_del_first(&c->free_by_rcu_ttrace); if (!obj) break; add_obj_to_free_list(c, obj); @@ -278,7 +272,7 @@ static void enque_to_free(struct bpf_mem_cache *c, void *obj) /* bpf_mem_cache is a per-cpu object. Freeing happens in irq_work. * Nothing races to add to free_by_rcu_ttrace list. */ - if (__llist_add(llnode, &c->free_by_rcu_ttrace)) + if (llist_add(llnode, &c->free_by_rcu_ttrace)) c->free_by_rcu_ttrace_tail = llnode; } @@ -290,7 +284,7 @@ static void do_call_rcu_ttrace(struct bpf_mem_cache *c) return; WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp_ttrace)); - llnode = __llist_del_all(&c->free_by_rcu_ttrace); + llnode = llist_del_all(&c->free_by_rcu_ttrace); if (llnode) /* There is no concurrent __llist_add(waiting_for_gp_ttrace) access. * It doesn't race with llist_del_all either. @@ -303,16 +297,22 @@ static void do_call_rcu_ttrace(struct bpf_mem_cache *c) * If RCU Tasks Trace grace period implies RCU grace period, free * these elements directly, else use call_rcu() to wait for normal * progs to finish and finally do free_one() on each element. + * + * call_rcu_tasks_trace() enqueues to a global queue, so it's ok + * that current cpu bpf_mem_cache != target bpf_mem_cache. */ call_rcu_tasks_trace(&c->rcu_ttrace, __free_rcu_tasks_trace); } static void free_bulk(struct bpf_mem_cache *c) { + struct bpf_mem_cache *tgt = c->tgt; struct llist_node *llnode, *t; unsigned long flags; int cnt; + WARN_ON_ONCE(tgt->unit_size != c->unit_size); + do { if (IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_save(flags); @@ -326,13 +326,13 @@ static void free_bulk(struct bpf_mem_cache *c) if (IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_restore(flags); if (llnode) - enque_to_free(c, llnode); + enque_to_free(tgt, llnode); } while (cnt > (c->high_watermark + c->low_watermark) / 2); /* and drain free_llist_extra */ llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra)) - enque_to_free(c, llnode); - do_call_rcu_ttrace(c); + enque_to_free(tgt, llnode); + do_call_rcu_ttrace(tgt); } static void bpf_mem_refill(struct irq_work *work) @@ -431,6 +431,7 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu) c->unit_size = unit_size; c->objcg = objcg; c->percpu_size = percpu_size; + c->tgt = c; prefill_mem_cache(c, cpu); } ma->cache = pc; @@ -453,6 +454,7 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu) c = &cc->cache[i]; c->unit_size = sizes[i]; c->objcg = objcg; + c->tgt = c; prefill_mem_cache(c, cpu); } } @@ -471,7 +473,7 @@ static void drain_mem_cache(struct bpf_mem_cache *c) * Except for waiting_for_gp_ttrace list, there are no concurrent operations * on these lists, so it is safe to use __llist_del_all(). */ - free_all(__llist_del_all(&c->free_by_rcu_ttrace), percpu); + free_all(llist_del_all(&c->free_by_rcu_ttrace), percpu); free_all(llist_del_all(&c->waiting_for_gp_ttrace), percpu); free_all(__llist_del_all(&c->free_llist), percpu); free_all(__llist_del_all(&c->free_llist_extra), percpu); @@ -605,8 +607,10 @@ static void notrace *unit_alloc(struct bpf_mem_cache *c) local_irq_save(flags); if (local_inc_return(&c->active) == 1) { llnode = __llist_del_first(&c->free_llist); - if (llnode) + if (llnode) { cnt = --c->free_cnt; + *(struct bpf_mem_cache **)llnode = c; + } } local_dec(&c->active); local_irq_restore(flags); @@ -630,6 +634,12 @@ static void notrace unit_free(struct bpf_mem_cache *c, void *ptr) BUILD_BUG_ON(LLIST_NODE_SZ > 8); + /* + * Remember bpf_mem_cache that allocated this object. + * The hint is not accurate. + */ + c->tgt = *(struct bpf_mem_cache **)llnode; + local_irq_save(flags); if (local_inc_return(&c->active) == 1) { __llist_add(llnode, &c->free_llist);