Re: [patch 2/4] net: Percpufy frequently used variables -- struct proto.memory_allocated

[Eric Dumazet <dada1@cosmosbay.com>]

Ravikiran G Thirumalai a écrit :
> Change struct proto->memory_allocated to a batching per-CPU counter 
> (percpu_counter) from an atomic_t.  A batching counter is better than a 
> plain per-CPU counter as this field is read often.
>
> Signed-off-by: Pravin B. Shelar <pravins@calsoftinc.com>
> Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
> Signed-off-by: Shai Fultheim <shai@scalex86.org>

Hello Ravikiran

I like this patch, but I'm not sure current percpu_counter fits the needs.

The percpu_counter_read() can return a value that is off by +-
FBC_BATCH*NR_CPUS, ie 2*(NR_CPUS^2) or 4*(NR_CPUS^2)

if NR_CPUS = 128, the 'error' from percpu_counter_read() is +- 32768

Is it acceptable ?

Thank you
Eric
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