Re: [PATCH] change cpuacct usage percpu format v2

[Ken Chen]

On Thu, Feb 26, 2009 at 11:29 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>
> 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.

- Ken
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