linux-kernel - Re: [PATCH] init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF

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Message-ID: <20200811075619.GE6215@alley>
Date:   Tue, 11 Aug 2020 09:56:19 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        "Luis R . Rodriguez" <mcgrof@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT
 description

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@...e.com>
> Cc: linux-kernel@...r.kernel.org
> Fixes: 23b2899f7f ("printk: allow increasing the ring buffer depending on the number of CPUs")
> Signed-off-by: Paul Menzel <pmenzel@...gen.mpg.de>

Great catch.

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr