[dm-devel] [PATCH] Fix I/O counts in vmstat

Jun'ichi Nomura j-nomura at ce.jp.nec.com
Wed Mar 21 10:04:08 UTC 2012

Hi Mikulas,

> The decision whether bio is counted or not is made by the code that
> submits the bio. This leads to some problems:

How about convering dm targets to use generic_make_request?

Since submit_bio counts vm events, it seems natural for
caller to decide which function to use.
Device driver does not know whether the requested I/O is
for vm-to-device or device-to-device.
We could still use iostat to measure throughput of individual
block devices. 

Jun'ichi Nomura, NEC Corporation

More information about the dm-devel mailing list