On Thursday 25 May 2006 12:59, Phil Dibowitz wrote: > On Thu, May 25, 2006 at 08:05:37AM -0500, Brent Cook wrote: > > > I'll admit to not knowing all the intricacies of the kernel coding > > > involved, but I don't offhand see how zeroing the stats would be > > > significantly more complex than updating the stats during normal usage. > > > But I'll have to leave that argument to the experts. > > > > What it boils down to is that currently, a single CPU or thread ever > > touches the stats concurrently, so it doesn't have to lock them or do > > anything special to ensure that the continue incrementing. If you want to > > make sure that the statistics actually reset when you want them to, you > > have to account for this case: > > > > CPU0 reads current value from memory (increment) > > CPU1 writes 0 to current value in memory (reset) > > CPU0 writes incremented value to memory (increment complete) > > Perhaps I'm missing something here, but these counters are only incrimented > in hardware... i.e. attomically. >
No, you're right - I'm just thinking that once one driver has this ability, users are going to want it for all network devices, and implementation on some devices (namely virtual ones - lo, tun, tap, br, vlan) is trickier than just setting a register. Some hardware devices too - mv643xx_eth.c just increments the network stats in software, for instance. Lockless software reset is fine though as long as people understand the consequences - it's absolutely fine, given the way I would use reset in my environment, MMV. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
