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

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On Friday 04 July 2003 05:47, Jan-Benedict Glaw wrote:
<snip>

Well... I don't really like to break userspace, but why don't we simply
make packet/traffic counters long long / u_int64_t? This way, we'd
simply keep almost all drivers untouched and only need to fiddle with
some sprints()/printk() statements?

I'm no hardware expert, however, that approach contains potential race 
condition - not a system critical one, but something we should be concerned 
about. 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...

Really, how many programs use the current statistics? I'd prefer to
modify them over adding strange patches like this one to the kernel...

I believe that on any kind of router some at some point in time would like to 
know the data transfered.

Jeff.

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