From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx176.postini.com [74.125.245.176]) by kanga.kvack.org (Postfix) with SMTP id 3BCCE6B0005 for ; Mon, 8 Apr 2013 21:29:07 -0400 (EDT) Message-ID: <51636EAC.10307@huawei.com> Date: Tue, 9 Apr 2013 09:28:12 +0800 From: Li Zefan MIME-Version: 1.0 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 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org 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, 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