linux-kernel - Re: [PATCH 1/2] workqueue: update numa affinity info at node hotplug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54B5D8B4.7010708@cn.fujitsu.com>
Date:	Wed, 14 Jan 2015 10:47:16 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ishimatsu, Yasuaki/石松 靖章" 
	<isimatu.yasuaki@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	"guz.fnst@...fujitsu.com" <guz.fnst@...fujitsu.com>
Subject: Re: [PATCH 1/2] workqueue: update numa affinity info at node hotplug

On 01/13/2015 11:22 PM, Tejun Heo wrote:
> Hello,
> 
> On Tue, Jan 13, 2015 at 03:19:09PM +0800, Lai Jiangshan wrote:
>> The Mapping of the *online* cpus to nodes is already maintained by numa code.
>>
>> What the workqueue needs is a special Mapping:
>> 	The Mapping of the *possible* cpus to nodes
>>
>> But this mapping (if the numa code maintain it) is a trouble:
>> 	"possible" implies the mapping is stable/constant/immutable, it is hard to
>> 	ensure it in the numa code.
>>
>> if mutability of this mapping is acceptable, we just move 20~40 LOC
>> of code from workqueue to numa code, all the other complexities
>> about it are still in workqueue.c.
> 
> Make numa code maintain the mapping to the best of its knowledge and
> invoke notification callbacks when it changes.  

The best of its knowledge is the physical onlined nodes and CPUs.
The cpu_present_mask can represent this knowledge. But it lacks of
the per-node cpu_present_mask and the notification callbacks.

> Even if that involves slightly more code, that's the right thing to do at this point.

Right, but in currently, the workqueue will be the only user, and I don't known
asking who to do it, so I may keep it in the workqueue.c.

> This puts the logic which is complicated by the fact that the mapping may
> change where it's caused not some random unrelated place.  


> It'd be
> awesome if somebody more familiar with the numa side can chime in and
> explain why this mapping change can't be avoided.

I'm also looking for someone answer it.

> 
> Thanks.
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/