From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id B02A36B0033 for ; Sat, 14 Jan 2017 08:19:53 -0500 (EST) Received: by mail-lf0-f71.google.com with SMTP id j90so4004810lfi.3 for ; Sat, 14 Jan 2017 05:19:53 -0800 (PST) Received: from smtp44.i.mail.ru (smtp44.i.mail.ru. [94.100.177.104]) by mx.google.com with ESMTPS id x10si9831616lfd.263.2017.01.14.05.19.51 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sat, 14 Jan 2017 05:19:51 -0800 (PST) Date: Sat, 14 Jan 2017 16:19:39 +0300 From: Vladimir Davydov Subject: Re: [PATCH 2/9] slab: remove synchronous rcu_barrier() call in memcg cache release path Message-ID: <20170114131939.GA2668@esperanza> References: <20170114055449.11044-1-tj@kernel.org> <20170114055449.11044-3-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170114055449.11044-3-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, jsvana@fb.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@fb.com Hello Tejun, Thanks a lot for looking into this issue as it seems to affect a lot of users! On Sat, Jan 14, 2017 at 12:54:42AM -0500, Tejun Heo wrote: > This patch updates the cache release path so that it simply uses > call_rcu() instead of the synchronous rcu_barrier() + custom batching. > This doesn't cost more while being logically simpler and way more > scalable. The point of rcu_barrier() is to wait until all rcu calls freeing slabs from the cache being destroyed are over (rcu_free_slab, kmem_rcu_free). I'm not sure if call_rcu() guarantees that for all rcu implementations too. If it did, why would we need rcu_barrier() at all? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org