Re: [PATCH v8 4/4] printk: allow increasing the ring buffer depending on the number of CPUs

[Luis R. Rodriguez]

On Mon, Jun 23, 2014 at 03:41:34PM -0700, Andrew Morton wrote:
> On Wed, 18 Jun 2014 13:45:37 -0700 "Luis R. Rodriguez" <mcgrof@xxxxxxxxxxxxxxxx> wrote:
> 
> > ...
> >
> > If an increase is required the ring buffer is increased to
> > +	  the next power of 2 that can fit both the minimum kernel ring buffer
> > +	  (LOG_BUF_SHIFT) plus the additional worst case CPU contributions.
> >
> > ...
> >
> > +	log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
> > +}
> 
> I'd have expected
> 
>   total_cpu_space = minimum-per-cpu-len * nr_possible_cpus;
>   log_buf_len = max(__LOG_BUF_LEN, total_cpu_space)
> 
> but here you added __LOG_BUF_LEN to total_cpu_space and I cannot work
> out why.  
> .

Ah, because its cpu_extra, not total_cpu_space that is being
computed, the goal was to see how much extra junk on the
worst case a CPU might contribute. The __LOG_BUF_LEN is the
default size, so we combine both.

  Luis
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