Re: [PATCH - RFC] [1/5] 64-bit network statistics - generic net

[Bernd Eckenfels <ecki@calista.eckenfels.6bone.ka-ip.net>]

In article <200307041357.32871.jeffpc@optonline.net> you wrote:
> If one cpu tries to read a u_int64_t variable while another tries to 
> update it, the worst case scenario is that the reader will get the high 
> 32-bits before the write, and low 32-bit after the write, now if the counter 
> overflow, the number would be off by 4GB! (This only applies to 32-bit 
> architectures.) True, there are cache coherency algorithms, etc...

a reader like ifconfig can easyly work around this with multiple tries, but
incremeting those variables wont work that easy, and therefore needs a lock,
which will be a major pita.

64bit counters should be a result of lockless per-cpu network counters
(32bit) with some kind of async merging.

Or we wait till 64bit hardware is more common :)

Greetings
Bernd
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