From: Glauber Costa <glommer@parallels.com>
To: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizefan@huawei.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 13/12] memcg: don't need memcg->memcg_name
Date: Tue, 9 Apr 2013 11:55:07 +0400 [thread overview]
Message-ID: <5163C95B.8010502@parallels.com> (raw)
In-Reply-To: <51638F2B.3000800@jp.fujitsu.com>
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.
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next prev parent reply other threads:[~2013-04-09 7:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 6:32 [PATCH 0/12][V2] memcg: make memcg's life cycle the same as cgroup Li Zefan
2013-04-08 6:33 ` [PATCH 01/12] memcg: take reference before releasing rcu_read_lock Li Zefan
2013-04-08 6:33 ` [PATCH 02/12] memcg: avoid accessing memcg after releasing reference Li Zefan
2013-04-08 6:33 ` [PATCH 03/12] Revert "memcg: avoid dangling reference count in creation failure." Li Zefan
2013-04-09 2:50 ` Kamezawa Hiroyuki
2013-04-08 6:33 ` [PATCH 04/12] memcg, kmem: fix reference count handling on the error path Li Zefan
2013-04-09 2:51 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 05/12] memcg: use css_get() in sock_update_memcg() Li Zefan
2013-04-08 6:34 ` [PATCH 06/12] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Li Zefan
2013-04-09 2:53 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 07/12] memcg: use css_get/put when charging/uncharging kmem Li Zefan
2013-04-08 14:14 ` Michal Hocko
2013-04-09 2:55 ` Kamezawa Hiroyuki
2013-04-08 6:34 ` [PATCH 08/12] memcg: use css_get/put for swap memcg Li Zefan
2013-04-08 6:35 ` [PATCH 09/12] cgroup: make sure parent won't be destroyed before its children Li Zefan
2013-04-08 15:36 ` Tejun Heo
2013-04-08 6:35 ` [PATCH 10/12] memcg: don't need to get a reference to the parent Li Zefan
2013-04-08 6:36 ` [PATCH 11/12] memcg: kill memcg refcnt Li Zefan
2013-04-08 6:36 ` [PATCH 12/12] memcg: don't need to free memcg via RCU or workqueue Li Zefan
2013-04-08 14:15 ` Michal Hocko
2013-04-09 2:57 ` Kamezawa Hiroyuki
2013-04-08 6:36 ` [PATCH 13/12] memcg: don't need memcg->memcg_name Li Zefan
2013-04-08 14:25 ` Michal Hocko
2013-04-09 1:28 ` Li Zefan
2013-04-09 3:10 ` Kamezawa Hiroyuki
2013-04-09 3:18 ` Li Zefan
2013-04-09 3:46 ` Kamezawa Hiroyuki
2013-04-09 7:55 ` Glauber Costa [this message]
2013-04-09 3:59 ` Tejun Heo
2013-04-09 7:53 ` Glauber Costa
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