linux-kernel - Re: [PATCH] change cpuacct usage percpu format v2

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]

Date:	Sat, 28 Feb 2009 08:34:02 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	"Ken Chen" <kenchen@...gle.com>
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"menage@...gle.com" <menage@...gle.com>,
	"lizf@...fujitsu.com" <lizf@...fujitsu.com>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	mingo@...e.hu,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] change cpuacct usage percpu format v2

Ken Chen さんは書きました：
> On Thu, Feb 26, 2009 at 11:29 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> wrote:
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>> cpuacct.usage_percpu shows per cpu usage information via cgroupfs.
>> It shows all "present" cpus information and "whose information ?"
>> is explained just by index of data implicitly.
>>
>> IIRC, there is physical cpu hotplug system and it can remove
>> cpus and change map. Considering a software which records
>> this information pediodically(like sar), its better to show id of cpu
>> in explict way.
>
> The new format carries a lot of overhead.  I would think user space
> software can record /sys/devices/system/cpu/present and use that to
> map cpu index.
>
"a lot of" ? I talking about cpu hotplug and reading another file as
/sys/devices/system/cpu/present every time before reading this file
gives much much much more overhead ;)

A program which handles this kind of information tend to ignore hotplug
event and continue to use informaton which it gathers at start-up and
will not see updated information....as libnuma etc.

Thanks,
-Kame



--
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/