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Move if_opackets++ to where if_obytes are
Hi,
I propose to move if_opackets from device drivers to where
if_obytes is incremented (not just one place), for example
in if_transmit.
The aims of the change are:
- Unify how it's incremented
- Usages of the counter are different between device
drivers
- There are roughly two places to count it up;
(1) when a packet is dequeued from if_snd (in
XXX_start function) and (2) when a packet is
successfully transmitted (in Tx interrupt)
- Users normally expect the counter is incremented in the
same manner between device drivers
- It is hard to unify the behavior while having the counter
in each device driver
- Synchronize with if_obytes
- Users normally expect if_opackets and if_obytes are
synchronized, but they aren't now
- It is hard to do so while having the two counters in
different places
- Simplify the code
- We can reduce the number of places doing if_opackets++
Some concerns on the change:
- The meaning/behavior of the counter is changed
- From "the number of packets sent on the interface" to
"the number of packets passed to the interface to send"
- But if_obytes is ever like that
- if_oerrors isn't moved (at least in this change)
- It is hard to count errors happening in a device
driver outside the device driver
- We can count the number of dropped packets at the if_snd
queue but that's perhaps not what we want to know
by if_oerrors
- That aside IMO errors happening in a device driver should
be counted by driver own statistic counters and be
reported via sysctl, evcnt or the like
- So we can know what kind of errors happened, not just
some sort of errors happened
This is a patch of the change:
http://www.netbsd.org/~ozaki-r/move-if_opackets.diff
The patch includes only changes for sys/net*, wm(4) and
vioif(4). Changes for other drivers will be made once the
proposal is accepted.
Any comments or suggestions?
Thanks,
ozaki-r
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