Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936687Ab3DIB24 (ORCPT ); Mon, 8 Apr 2013 21:28:56 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:16220 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936573Ab3DIB2z (ORCPT ); Mon, 8 Apr 2013 21:28:55 -0400 Message-ID: <51636EAC.10307@huawei.com> Date: Tue, 9 Apr 2013 09:28:12 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Michal Hocko CC: Andrew Morton , Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , Subject: Re: [PATCH 13/12] memcg: don't need memcg->memcg_name References: <5162648B.9070802@huawei.com> <51626584.7050405@huawei.com> <20130408142503.GH17178@dhcp22.suse.cz> In-Reply-To: <20130408142503.GH17178@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2044 Lines: 57 On 2013/4/8 22:25, Michal Hocko wrote: > On Mon 08-04-13 14:36:52, Li Zefan wrote: > [...] >> @@ -5188,12 +5154,28 @@ static int mem_cgroup_dangling_read(struct cgroup *cont, struct cftype *cft, >> struct seq_file *m) >> { >> struct mem_cgroup *memcg; >> + char *memcg_name; >> + int ret; > > The interface is only for debugging, all right, but that doesn't mean we > should allocate a buffer for each read. Why cannot we simply use > cgroup_path for seq_printf directly? Can we still race with the group > rename? because cgroup_path() requires the caller pass a buffer to it. > >> + >> + /* >> + * cgroup.c will do page-sized allocations most of the time, >> + * so we'll just follow the pattern. Also, __get_free_pages >> + * is a better interface than kmalloc for us here, because >> + * we'd like this memory to be always billed to the root cgroup, >> + * not to the process removing the memcg. While kmalloc would >> + * require us to wrap it into memcg_stop/resume_kmem_account, >> + * with __get_free_pages we just don't pass the memcg flag. >> + */ >> + memcg_name = (char *)__get_free_pages(GFP_KERNEL, 0); >> + if (!memcg_name) >> + return -ENOMEM; >> >> mutex_lock(&dangling_memcgs_mutex); >> >> list_for_each_entry(memcg, &dangling_memcgs, dead) { >> - if (memcg->memcg_name) >> - seq_printf(m, "%s:\n", memcg->memcg_name); >> + ret = cgroup_path(memcg->css.cgroup, memcg_name, PAGE_SIZE); >> + if (!ret) >> + seq_printf(m, "%s:\n", memcg_name); >> else >> seq_printf(m, "%p (name lost):\n", memcg); >> >> @@ -5203,6 +5185,7 @@ static int mem_cgroup_dangling_read(struct cgroup *cont, struct cftype *cft, >> } >> >> mutex_unlock(&dangling_memcgs_mutex); >> + free_pages((unsigned long)memcg_name, 0); >> return 0; >> } >> #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/