From: Paul Menzel Date: Tue, 11 Aug 2020 09:29:23 +0000 (+0200) Subject: init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0f7636e1654338c34e3c220c02b2ffad78b6ccc0;p=linux.git init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description 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. Fixes: 23b2899f7f194f06e ("printk: allow increasing the ring buffer depending on the number of CPUs") Cc: Luis R. Rodriguez Cc: linux-kernel@vger.kernel.org Signed-off-by: Paul Menzel Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20200811092924.6256-1-pmenzel@molgen.mpg.de --- diff --git a/init/Kconfig b/init/Kconfig index c9446911cf41e..02d13ae27abb9 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -719,7 +719,7 @@ config LOG_CPU_MAX_BUF_SHIFT with more CPUs. Therefore this value is used only when the sum of contributions is greater than the half of the default kernel ring buffer as defined by LOG_BUF_SHIFT. The default values are set - so that more than 64 CPUs are needed to trigger the allocation. + so that more than 16 CPUs are needed to trigger the allocation. Also this option is ignored when "log_buf_len" kernel parameter is used as it forces an exact (power of two) size of the ring buffer.