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From: Richard Weinberger <richard-/L3Ra7n9ekc@public.gmane.org>
To: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
	mhocko-AlSwsSmVLrQ@public.gmane.org,
	bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org,
	akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
	vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org,
	tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	handai.szj-3b8fjiQLQpfQT0dZR+AlfA@public.gmane.org,
	rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org,
	kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 05 Jun 2014 18:10:17 +0200	[thread overview]
Message-ID: <53909669.8000007@nod.at> (raw)
In-Reply-To: <20140605160029.GA28812-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Am 05.06.2014 18:00, schrieb Oleg Nesterov:
> On 06/05, Richard Weinberger wrote:
>>
>> Am 05.06.2014 16:18, schrieb Oleg Nesterov:
>>> On 06/05, Richard Weinberger wrote:
>>>>
>>>> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
>>>> +{
>>>> +	int ret = 0;
>>>> +
>>>> +	if (!memcg)
>>>> +		goto out;
>>>> +
>>>> +	spin_lock(&memcg_oom_lock);
>>>> +	ret = !list_empty(&memcg->oom_notify);
>>>> +	spin_unlock(&memcg_oom_lock);
>>>> +
>>>> +out:
>>>> +	return ret;
>>>> +}
>>>
>>> Do we really need memcg_oom_lock to check list_empty() ? With or without
>>> this lock we can race with list_add/del anyway, and I guess we do not care.
>>
>> Hmm, in mm/memcontrol.c all list_dev/add are under memcg_oom_lock.
> 
> And? How this lock can help to check list_empty() ?
> 
> list_add/del can come right after mem_cgroup_has_listeners() and change
> the value of list_empty() anyway.

Ahh, now I can follow your mind. :)

Thanks,
//richard

WARNING: multiple messages have this Message-ID (diff)
From: Richard Weinberger <richard@nod.at>
To: Oleg Nesterov <oleg@redhat.com>
Cc: hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com,
	kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
	vdavydov@parallels.com, tj@kernel.org, handai.szj@taobao.com,
	rientjes@google.com, rusty@rustcorp.com.au,
	kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
	cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 05 Jun 2014 18:10:17 +0200	[thread overview]
Message-ID: <53909669.8000007@nod.at> (raw)
In-Reply-To: <20140605160029.GA28812@redhat.com>

Am 05.06.2014 18:00, schrieb Oleg Nesterov:
> On 06/05, Richard Weinberger wrote:
>>
>> Am 05.06.2014 16:18, schrieb Oleg Nesterov:
>>> On 06/05, Richard Weinberger wrote:
>>>>
>>>> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
>>>> +{
>>>> +	int ret = 0;
>>>> +
>>>> +	if (!memcg)
>>>> +		goto out;
>>>> +
>>>> +	spin_lock(&memcg_oom_lock);
>>>> +	ret = !list_empty(&memcg->oom_notify);
>>>> +	spin_unlock(&memcg_oom_lock);
>>>> +
>>>> +out:
>>>> +	return ret;
>>>> +}
>>>
>>> Do we really need memcg_oom_lock to check list_empty() ? With or without
>>> this lock we can race with list_add/del anyway, and I guess we do not care.
>>
>> Hmm, in mm/memcontrol.c all list_dev/add are under memcg_oom_lock.
> 
> And? How this lock can help to check list_empty() ?
> 
> list_add/del can come right after mem_cgroup_has_listeners() and change
> the value of list_empty() anyway.

Ahh, now I can follow your mind. :)

Thanks,
//richard

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WARNING: multiple messages have this Message-ID (diff)
From: Richard Weinberger <richard@nod.at>
To: Oleg Nesterov <oleg@redhat.com>
Cc: hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com,
	kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
	vdavydov@parallels.com, tj@kernel.org, handai.szj@taobao.com,
	rientjes@google.com, rusty@rustcorp.com.au,
	kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
	cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 05 Jun 2014 18:10:17 +0200	[thread overview]
Message-ID: <53909669.8000007@nod.at> (raw)
In-Reply-To: <20140605160029.GA28812@redhat.com>

Am 05.06.2014 18:00, schrieb Oleg Nesterov:
> On 06/05, Richard Weinberger wrote:
>>
>> Am 05.06.2014 16:18, schrieb Oleg Nesterov:
>>> On 06/05, Richard Weinberger wrote:
>>>>
>>>> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
>>>> +{
>>>> +	int ret = 0;
>>>> +
>>>> +	if (!memcg)
>>>> +		goto out;
>>>> +
>>>> +	spin_lock(&memcg_oom_lock);
>>>> +	ret = !list_empty(&memcg->oom_notify);
>>>> +	spin_unlock(&memcg_oom_lock);
>>>> +
>>>> +out:
>>>> +	return ret;
>>>> +}
>>>
>>> Do we really need memcg_oom_lock to check list_empty() ? With or without
>>> this lock we can race with list_add/del anyway, and I guess we do not care.
>>
>> Hmm, in mm/memcontrol.c all list_dev/add are under memcg_oom_lock.
> 
> And? How this lock can help to check list_empty() ?
> 
> list_add/del can come right after mem_cgroup_has_listeners() and change
> the value of list_empty() anyway.

Ahh, now I can follow your mind. :)

Thanks,
//richard

  parent reply	other threads:[~2014-06-05 16:10 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-05 14:00 oom: Be less verbose Richard Weinberger
2014-06-05 14:00 ` Richard Weinberger
2014-06-05 14:00 ` [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners Richard Weinberger
2014-06-05 14:00   ` Richard Weinberger
2014-06-05 14:18   ` Oleg Nesterov
2014-06-05 14:18     ` Oleg Nesterov
     [not found]     ` <20140605141841.GA23796-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2014-06-05 15:46       ` Richard Weinberger
2014-06-05 15:46         ` Richard Weinberger
2014-06-05 15:46         ` Richard Weinberger
2014-06-05 16:00         ` Oleg Nesterov
2014-06-05 16:00           ` Oleg Nesterov
     [not found]           ` <20140605160029.GA28812-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2014-06-05 16:10             ` Richard Weinberger [this message]
2014-06-05 16:10               ` Richard Weinberger
2014-06-05 16:10               ` Richard Weinberger
2014-06-05 15:00   ` Michal Hocko
2014-06-05 15:00     ` Michal Hocko
2014-06-05 15:55     ` Richard Weinberger
2014-06-05 15:55       ` Richard Weinberger
2014-06-05 16:18       ` Michal Hocko
2014-06-05 16:18         ` Michal Hocko
     [not found]         ` <20140605161807.GD15939-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2014-06-05 21:58           ` Richard Weinberger
2014-06-05 21:58             ` Richard Weinberger
2014-06-05 21:58             ` Richard Weinberger
2014-06-05 21:01     ` David Rientjes
2014-06-05 21:01       ` David Rientjes
2014-06-06  9:10       ` Michal Hocko
2014-06-06  9:10         ` Michal Hocko

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