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@xxxxxxxxxxxxx> (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@xxxxxxxx> > Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@xxxxxxxxxxxxxx/ > Reported-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> > Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@xxxxxxxxxx/ > Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> Best Regards, Petr
