On Wed, 2006-12-27 at 09:44 -0500, jamal wrote:

On Wed, 2006-27-12 at 14:08 +0100, Arjan van de Ven wrote:

quoted

sure; however the kernel doesn't provide more accurate information
currently (and I doubt it could even, it's not so easy to figure out
which interface triggered the softirq if 2 interfaces share the cpu, and
then, how much work came from which etc).

If you sample CPU use and in between two samples you are able to know
which nic is tied to which CPU, how much cycles such cpu consumed in
user vs kernel, and how many packets were seen on such nic; then you
should have the info necessary to make a decision, no?

Note that getting softirq time itself isn't a problem, that is available
actually. (it's not very accurate but that's another kettle of fish
entirely)

But... No that isn't better than packet counts.
Cases where it simply breaks 
1) you have more nics than cpus, so you HAVE to have sharing 
2) Other loads going on than just pure networking (storage but also
timers and .. and ..)

And neither is even remotely artificial. 

Yes, I know it is
a handwave on my part and it is complex but by the same token, I would
suspect each kind of IO derived work (which results in interupts) will
have more inputs that could help you make a proper decision than a mere
glance of the interupts. I understand for example the SCSI subsystem
these days behaves very much like NAPI.

the difference between scsi and networking is that the work scsi does
per "sector" is orders and orders of magnitude less than what networking
does. SCSI does it's work mostly per "transfer" not per sector, and if
you're busy you tend to get larger transfers as well (megabytes is not
special). SCSI also doesn't look at the payload at all, unlike
networking (where there are those pesky headers every 1500 bytes or less
that the kernel needs to look at :)

It is certainly much more promising now than before. Most people will
probably have symettrical type of apps, so it should work for them.
For someone like myself i will still not use it because i typically dont
have symettrical loads.

unless you have more nics than you have cpus, irqbalance will do the
right thing anyway (it'll tend to not share or move networking
interrupts). And once you have more nics than you have cpus.... see
above.

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