Commit 0f7636e1 authored Aug 11, 2020 by Paul Menzel Committed by Petr Mladek Nov 03, 2020

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: 23b2899f ("printk: allow increasing the ring buffer depending on the number of CPUs")
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200811092924.6256-1-pmenzel@molgen.mpg.de

parent 8119c433

init/Kconfig

+1 −1

Original line number	Diff line number	Diff line
		@@ -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.

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