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From: Xishi Qiu <qiuxishi@huawei.com>
To: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tang Chen <tangchen@cn.fujitsu.com>,
	Yinghai Lu <yinghai@kernel.org>, Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Toshi Kani <toshi.kani@hp.com>, Mel Gorman <mgorman@suse.de>,
	Tejun Heo <tj@kernel.org>, Xiexiuqi <xiexiuqi@huawei.com>,
	Hanjun Guo <guohanjun@huawei.com>, Li Zefan <lizefan@huawei.com>
Subject: Re: node-hotplug: is memset 0 safe in try_offline_node()?
Date: Wed, 4 Mar 2015 10:52:38 +0800	[thread overview]
Message-ID: <54F67376.8050001@huawei.com> (raw)
In-Reply-To: <54F66C52.4070600@huawei.com>

On 2015/3/4 10:22, Xishi Qiu wrote:

> On 2015/3/3 18:20, Gu Zheng wrote:
> 
>> Hi Xishi,
>> On 03/03/2015 11:30 AM, Xishi Qiu wrote:
>>
>>> When hot-remove a numa node, we will clear pgdat,
>>> but is memset 0 safe in try_offline_node()?
>>
>> It is not safe here. In fact, this is a temporary solution here.
>> As you know, pgdat is accessed lock-less now, so protection
>> mechanism (RCUi 1/4 ?) is needed to make it completely safe here,
>> but it seems a bit over-kill.
>>

Hi Gu,

Can we just remove "memset(pgdat, 0, sizeof(*pgdat));" ?
I find this will be fine in the stress test except the warning 
when hot-add memory.

Thanks,
Xishi Qiu

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WARNING: multiple messages have this Message-ID (diff)
From: Xishi Qiu <qiuxishi@huawei.com>
To: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tang Chen <tangchen@cn.fujitsu.com>,
	Yinghai Lu <yinghai@kernel.org>, Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Toshi Kani <toshi.kani@hp.com>, Mel Gorman <mgorman@suse.de>,
	Tejun Heo <tj@kernel.org>, Xiexiuqi <xiexiuqi@huawei.com>,
	Hanjun Guo <guohanjun@huawei.com>, Li Zefan <lizefan@huawei.com>
Subject: Re: node-hotplug: is memset 0 safe in try_offline_node()?
Date: Wed, 4 Mar 2015 10:52:38 +0800	[thread overview]
Message-ID: <54F67376.8050001@huawei.com> (raw)
In-Reply-To: <54F66C52.4070600@huawei.com>

On 2015/3/4 10:22, Xishi Qiu wrote:

> On 2015/3/3 18:20, Gu Zheng wrote:
> 
>> Hi Xishi,
>> On 03/03/2015 11:30 AM, Xishi Qiu wrote:
>>
>>> When hot-remove a numa node, we will clear pgdat,
>>> but is memset 0 safe in try_offline_node()?
>>
>> It is not safe here. In fact, this is a temporary solution here.
>> As you know, pgdat is accessed lock-less now, so protection
>> mechanism (RCU？) is needed to make it completely safe here,
>> but it seems a bit over-kill.
>>

Hi Gu,

Can we just remove "memset(pgdat, 0, sizeof(*pgdat));" ?
I find this will be fine in the stress test except the warning 
when hot-add memory.

Thanks,
Xishi Qiu


  reply	other threads:[~2015-03-04  2:53 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-03  3:30 node-hotplug: is memset 0 safe in try_offline_node()? Xishi Qiu
2015-03-03  3:30 ` Xishi Qiu
2015-03-03 10:20 ` Gu Zheng
2015-03-03 10:20   ` Gu Zheng
2015-03-04  2:22   ` Xishi Qiu
2015-03-04  2:22     ` Xishi Qiu
2015-03-04  2:52     ` Xishi Qiu [this message]
2015-03-04  2:52       ` Xishi Qiu
2015-03-04  3:56       ` Gu Zheng
2015-03-04  3:56         ` Gu Zheng
2015-03-04  8:03         ` Xishi Qiu
2015-03-04  8:03           ` Xishi Qiu
2015-03-04  8:53           ` Kamezawa Hiroyuki
2015-03-04  8:53             ` Kamezawa Hiroyuki
2015-03-04  9:53             ` Gu Zheng
2015-03-04  9:53               ` Gu Zheng
2015-03-04  3:53     ` Gu Zheng
2015-03-04  3:53       ` Gu Zheng
2015-03-04  7:01       ` Xishi Qiu
2015-03-04  7:01         ` Xishi Qiu
2015-03-04  8:31       ` Xie XiuQi
2015-03-04  8:31         ` Xie XiuQi
2015-03-05  8:26 ` Gu Zheng
2015-03-05  8:26   ` Gu Zheng
2015-03-05  9:39   ` Xishi Qiu
2015-03-05  9:39     ` Xishi Qiu
2015-03-05  9:45     ` Gu Zheng
2015-03-05  9:45       ` Gu Zheng
2015-03-11  1:12     ` Gu Zheng
2015-03-11  1:12       ` Gu Zheng
2015-03-11  2:51       ` Xie XiuQi
2015-03-11  2:51         ` Xie XiuQi

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