From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id 42C6F6B0005 for ; Tue, 9 Apr 2013 03:54:25 -0400 (EDT) Message-ID: <5163C95B.8010502@parallels.com> Date: Tue, 9 Apr 2013 11:55:07 +0400 From: Glauber Costa 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> <5163868B.3020905@jp.fujitsu.com> <5163887D.1040809@huawei.com> <51638F2B.3000800@jp.fujitsu.com> In-Reply-To: <51638F2B.3000800@jp.fujitsu.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kamezawa Hiroyuki Cc: Li Zefan , Andrew Morton , Tejun Heo , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org On 04/09/2013 07:46 AM, Kamezawa Hiroyuki wrote: > (2013/04/09 12:18), 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; >>>> + >>>> + /* >>>> + * 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); >>>> >>> >>> I'm sorry for dawm question ...when this error happens ? >>> We may get ENAMETOOLONG even with PAGE_SIZE(>=4096bytes) buffer ? >>> >> >> It does no harm to check the return value, and we don't have to >> worry about if cgroup_path() will be changed to return some other >> errno like ENOMEM in the future. >> > Hmm. but the name is not lost, right ? > How about returning error rather than making a mixture of lines in different formats ? > I still think it would be preferable to dump as much informative data as we can. Even if the name is lost, a lot of info can still be present (from the caches, etc). The format also should not matter. Nobody will be script-processing this. -- 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