Re: [PATCH] init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description

From: Petr Mladek
Date: Tue Aug 11 2020 - 03:56:23 EST


On Tue 2020-08-11 09:31:45, Paul Menzel wrote:
> Currently, LOG_BUF_SHIFT defaults to 17, which is 2 ^ 17 bytes = 128 KB,
> and LOG_CPU_MAX_BUF_SHIFT defaults to 12, which is 2 ^ 12 bytes = 4 KB.
>
> Half of 128 KB is 64 KB, so more than 16 CPUs are required for the value
> to be used, as then the sum of contributions is greater than 64 KB for
> the first time. My guess is, that the description was written with the
> configuration values used in the SUSE in mind.
>
> Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Fixes: 23b2899f7f ("printk: allow increasing the ring buffer depending on the number of CPUs")
> Signed-off-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>

Great catch.

Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>

Best Regards,
Petr