From: Paul Menzel <pmenzel@molgen.mpg.de>
To: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>,
"Luis R . Rodriguez" <mcgrof@suse.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/2] init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description
Date: Tue, 11 Aug 2020 11:29:23 +0200 [thread overview]
Message-ID: <20200811092924.6256-1-pmenzel@molgen.mpg.de> (raw)
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: 23b2899f7f ("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
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
v2: Add Reviewed-by tag
init/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/init/Kconfig b/init/Kconfig
index d6a0b31b13dc..9dc607e3806f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -718,7 +718,7 @@ 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.
--
2.28.0
next reply other threads:[~2020-08-11 9:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-11 9:29 Paul Menzel [this message]
2020-08-11 9:29 ` [PATCH v2 2/2] init/Kconfig: Increase default log buffer size from 128 KB to 512 KB Paul Menzel
2020-08-11 10:53 ` Petr Mladek
2020-10-29 22:16 ` Paul Menzel
2020-10-30 15:28 ` Petr Mladek
2020-10-30 8:01 ` Geert Uytterhoeven
2020-10-30 16:00 ` [PATCH v2 1/2] init/Kconfig: Fix CPU number in LOG_CPU_MAX_BUF_SHIFT description Paul Menzel
2020-11-02 13:40 ` Petr Mladek
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