oo_req, rd_req, wr_req... cant find any docs

oo_req, rd_req, wr_req... cant find any docs

[Shaun Reitan]

I cannot seam to find any documentation on 
/sys/devices/vbd-<domid>-<##>/statistics/ and am trying to figure out 
what these stats represent.  From the looks of it rd_req means read 
requests.  Are these read requests that have already been completed? or 
can they be requests that are waiting/queued?

What is oo_req, all i can find on it is some comments about them being 
mysterious.

Another doc I found talks about rd_bytes but i don't see that, i do see 
rd_sect which i assume is sectors.  So is this whats meant for measuring 
how much has been transferred (assuming 512 bytes per sector)?


~ Shaun

Re: oo_req, rd_req, wr_req... cant find any docs

[Keir Fraser]

On 17/11/2010 19:38, "Shaun Reitan" <mailinglists@unix-scripts.com> wrote:

> I cannot seam to find any documentation on
> /sys/devices/vbd-<domid>-<##>/statistics/ and am trying to figure out
> what these stats represent.  From the looks of it rd_req means read
> requests.  Are these read requests that have already been completed? or
> can they be requests that are waiting/queued?

They count all requests since boot, including those for which processing has
not yet completed. Rd_req counts read requests, wr_req counts write
requests, oo_req counts the number of times that blkback paused consuming
requests because it is out of processing slots (not a massively interesting
stat to the user, probably).

> What is oo_req, all i can find on it is some comments about them being
> mysterious.
> 
> Another doc I found talks about rd_bytes but i don't see that, i do see
> rd_sect which i assume is sectors.  So is this whats meant for measuring
> how much has been transferred (assuming 512 bytes per sector)?

Yes an individual read/write request can span a large number of sectors.
Rd_sect/wr_sect tells you how much data has actually been transferred.

 -- Keir

> 
> ~ Shaun
> 
> 
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