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SubjectRe: 2.5 io statistics?
Larry McVoy <lm@bitmover.com> wrote:
>
> Is there a writeup of the changes anywhere? I'd like to port cstat to 2.5.
> Cstat is sort of a netstat/vmstat combo:
>
> load free cach swap pgin pgou dk0 dk1 dk2 dk3 ipkt opkt int ctx usr sys idl
> 0.00 19M 562M 48M 4.0K 12K 0 0 0 0 137 25 267 83 0 0 100
> 0.00 18M 563M 48M 0 12K 0 0 0 0 133 22 258 77 0 1 99

It's currently undergoing a bit of change.

In 2.5.67 all IO activity is monitored by opening and reading
/sys/block/hda/stat. This certainly doesn't scale when you have thousands of
disks, so there's a patch in -mm which performs runtime aggregation of global
stats and exposes that via /proc/diskstats.

So if you want to monitor the "global" IO activity, you don't need to open all
those sysfs files.

I don't know if the aggregate disk stats patch is ready to go yet. I'm
awaiting testing results, conversion of userspace tools, etc. I just plonked
it in there and haven't heard anything since.

As far as I know, neither the format of the sysfs file nor the format of
/proc/diskstats is documented anywhere.

Perhaps Rick can prepare a description for inclusion under Dcumentation/
somewhere?

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