Bibek, On Thu, Aug 10, 2023 at 09:54:51AM -0700, Andrew Morton wrote: > On Wed, 9 Aug 2023 18:46:40 +0530 Bibek Kumar Patro <quic_bibekkum@xxxxxxxxxxx> wrote: > > > Currently enabling CONFIG_CMA_DEBUG enables DEBUG preprocessor macro. > > If DEBUG is defined, it's equivalent to a printk with KERN_DEBUG loglevel > > flooding the dmesg buffer with pr_debug prints from mm/cma driver and from > > included files as well. This results in excessive amount of CMA logging and > > also might distract the debug teams with unrelated KERN_DEBUG prints.One of > > the ways engineers currently tackle this problem is by passing loglevel=N > > though commandline to suppress KERN_DEBUG messages. This approach can > > sometimes become tiresome due to its repetitive nature. > > This patch proposes an alternative approach by introducing a simple new > > config CONFIG_CMA_ALLOC_DEBUG which only shows the cma bit allocation > > status in case of cma failure and do not enable DEBUG preprocessor macro > > from CONFIG_CMA_DEBUG avoiding excessive CMA logging from pr_debug. > > Engineers and tech teams seeking only for bitmap status in case of cma > > failure can use this simple config instead of worrying about changing > > the loglevel or trying other similar workarounds. > > Would it be better to control this at runtime? With a /proc or /sys tunable? IIUC, Andrew is asking/suggesting that would a runtime knob be useful here? For ex: /proc/sys/vm/cma_dump_on_failure : This needs to be registerd in the cma.c . grep for "register_sysctl_init" in mm code. We can set this to true by default in case CMA_DEBUG is enabled so that current users are not affected. /sys/kernel/mm/cma/bitmap_dump_on_failure : This needs to stay in cma_sysfs.c code Thanks, Pavan
