Ming Zhang wrote:
On Sun, 2007-03-25 at 23:51 -0400, Alan D. Brunelle wrote:
Ming Zhang wrote:
from btt user guide
"Q2Q which measures the time between queue traces in the system.
This provides some idea as to how quickly IOs are being handed to
the block IO layer."
does this mean the time between queuing N request and N
+1 request?
Hi Ming -
This is the average time between the Q traces being logged. We take the
difference between each succeeding Q trace, and divide the sum by the total.
so like block layer idle indicator.
Not quite - the block layer %util value indicates how much the
underlying device (driver) has active commands. Q2Q is more of a measure
of upper-level activity - application & file system & VM (page cache).
It indicates how quickly commands are being submitted to the block IO layer.
maybe a similar D2D will be a nice
device indicator as well.
This would be an indicator of how quickly lower-layer device drivers are
getting issued IOs. It would be trivial to implement, if you are
interested in it, I can do it...
Alan
Alan
thanks!
Ming
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