| Message ID | 20240204232945.1576403-2-yoann.congal@smile.fr (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal | expand |
On Mon, Feb 5, 2024 at 8:30 AM Yoann Congal <yoann.congal@smile.fr> wrote: > > LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL: > config LOG_CPU_MAX_BUF_SHIFT > default 12 if !BASE_SMALL > default 0 if BASE_SMALL > But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always > evaluated to true whatever is the value of BASE_SMALL. > > This patch fixes this by using BASE_FULL (type bool) which is equivalent > to BASE_SMALL==0. > > Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to > CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will > not be a big impact due to this code in kernel/printk/printk.c: > /* by default this will only continue through for large > 64 CPUs */ > if (cpu_extra <= __LOG_BUF_LEN / 2) > return; > Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite > rare. > > John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote: > > For printk this will mean that BASE_SMALL systems were probably > > previously allocating/using the dynamic ringbuffer and now they will > > just continue to use the static ringbuffer. Which is fine and saves > > memory (as it should). > > Signed-off-by: Yoann Congal <yoann.congal@smile.fr> > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> > Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/ > Reported-by: Vegard Nossum <vegard.nossum@oracle.com> > Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/ > Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") > --- > init/Kconfig | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
On 2024-02-05, Yoann Congal <yoann.congal@smile.fr> wrote: > LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL: > config LOG_CPU_MAX_BUF_SHIFT > default 12 if !BASE_SMALL > default 0 if BASE_SMALL > But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always > evaluated to true whatever is the value of BASE_SMALL. > > This patch fixes this by using BASE_FULL (type bool) which is equivalent > to BASE_SMALL==0. > > Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to > CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will > not be a big impact due to this code in kernel/printk/printk.c: > /* by default this will only continue through for large > 64 CPUs */ > if (cpu_extra <= __LOG_BUF_LEN / 2) > return; > Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite > rare. > > John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote: >> For printk this will mean that BASE_SMALL systems were probably >> previously allocating/using the dynamic ringbuffer and now they will >> just continue to use the static ringbuffer. Which is fine and saves >> memory (as it should). > > Signed-off-by: Yoann Congal <yoann.congal@smile.fr> > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> > Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/ > Reported-by: Vegard Nossum <vegard.nossum@oracle.com> > Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/ > Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") Reviewed-by: John Ogness <john.ogness@linutronix.de>
On Mon 2024-02-05 00:29:44, Yoann Congal wrote: > LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL: > config LOG_CPU_MAX_BUF_SHIFT > default 12 if !BASE_SMALL > default 0 if BASE_SMALL > But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always > evaluated to true whatever is the value of BASE_SMALL. > > This patch fixes this by using BASE_FULL (type bool) which is equivalent > to BASE_SMALL==0. > > Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to > CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will > not be a big impact due to this code in kernel/printk/printk.c: > /* by default this will only continue through for large > 64 CPUs */ > if (cpu_extra <= __LOG_BUF_LEN / 2) > return; > Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite > rare. > > John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote: > > For printk this will mean that BASE_SMALL systems were probably > > previously allocating/using the dynamic ringbuffer and now they will > > just continue to use the static ringbuffer. Which is fine and saves > > memory (as it should). More precisely, it allocated the buffer dynamically when the sum of per-CPU-extra space exceeded half of the default static ring buffer. This happened for systems with more than 64 CPUs with the default config values. I believe that this patch won't have any effect in practice. It is hard to imagine a system with >64 CPUs which would require BASE_SMALL kernel. Well, never say never ;-) > Signed-off-by: Yoann Congal <yoann.congal@smile.fr> > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> > Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/ > Reported-by: Vegard Nossum <vegard.nossum@oracle.com> > Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/ > Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") Reviewed-by: Petr Mladek <pmladek@suse.com> Best Regards, Petr
diff --git a/init/Kconfig b/init/Kconfig index deda3d14135bb..73efb76f38734 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -734,8 +734,8 @@ config LOG_CPU_MAX_BUF_SHIFT int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" depends on SMP range 0 21 - default 12 if !BASE_SMALL - default 0 if BASE_SMALL + default 12 if BASE_FULL + default 0 depends on PRINTK help This option allows to increase the default ring buffer size
LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL: config LOG_CPU_MAX_BUF_SHIFT default 12 if !BASE_SMALL default 0 if BASE_SMALL But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always evaluated to true whatever is the value of BASE_SMALL. This patch fixes this by using BASE_FULL (type bool) which is equivalent to BASE_SMALL==0. Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will not be a big impact due to this code in kernel/printk/printk.c: /* by default this will only continue through for large > 64 CPUs */ if (cpu_extra <= __LOG_BUF_LEN / 2) return; Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite rare. John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote: > For printk this will mean that BASE_SMALL systems were probably > previously allocating/using the dynamic ringbuffer and now they will > just continue to use the static ringbuffer. Which is fine and saves > memory (as it should). Signed-off-by: Yoann Congal <yoann.congal@smile.fr> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/ Reported-by: Vegard Nossum <vegard.nossum@oracle.com> Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/ Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") --- init/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)