about profiling and stats info for pagecache/buffercache

about profiling and stats info for pagecache/buffercache

[Alexey Zhuravlev]

Hello!

As far as I understand, now Linux have no facility to collect stats info
for pagecache/buffercache. For example, it'd be fine if we can see how 
many requests were submited to pagecache/buffercache and how many of 
these requests was serviced from cache without I/O. Moreover, it'd be fine
to have some profiling info on requests for pagecache/buffercache...


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Re: about profiling and stats info for pagecache/buffercache

[Rik van Riel]

On Sun, 6 May 2001, Alexey Zhuravlev wrote:

> As far as I understand, now Linux have no facility to collect stats info
> for pagecache/buffercache. For example, it'd be fine if we can see how 
> many requests were submited to pagecache/buffercache and how many of 
> these requests was serviced from cache without I/O. Moreover, it'd be fine
> to have some profiling info on requests for pagecache/buffercache...

OK, so you want:

pagecache	nr_requests	hit	mis	
buffercache	nr_requests	hit	mis

I'd like to see a few other statistics as well, mainly for the
pageout code...

- nr pages scannned
- nr pages moved to the inactive_clean list
- nr pages "rescued" from the inactive_clean list
- nr pages evicted
- nr pages deactivated by pageout scanning
- nr pages deactivated by drop-behind

Are there any more ideas for statistics people would like to
see?

regards,

Rik
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Re: about profiling and stats info for pagecache/buffercache

[Stephen C. Tweedie]

Hi,

On Sun, May 06, 2001 at 04:42:04PM -0300, Rik van Riel wrote:
> 
> I'd like to see a few other statistics as well, mainly for the
> pageout code...
> 
> - nr pages scannned
> - nr pages moved to the inactive_clean list
> - nr pages "rescued" from the inactive_clean list
> - nr pages evicted
> - nr pages deactivated by pageout scanning
> - nr pages deactivated by drop-behind
> 
> Are there any more ideas for statistics people would like to
> see?

As long as that's per-zone, and includes failed scans as well as
successes, fine.

--Stephen
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