This patch adds the new Kconfig option CONFIG_CYCLIC_RATELIMIT_US which defines the min allowed time after with a new call into the cyclic infrastructure is allowed. This results in a rate limiting of the all functions hooked into the cyclic interface. As it's been noticed that on some platforms, that high frequent calls to schedule() (replaced from WATCHDOG_RESET) may lead to a performance degradation.

When a high frequent calling into schedule() is detected, a warning is logged only once to help indentify this frantic caller.

Signed-off-by: Stefan Roese sr@denx.de Cc: Simon Glass sjg@chromium.org Cc: Christophe Leroy christophe.leroy@csgroup.eu --- - Some spelling fixes (Simon) - Minor coding style improvement in comment (Simon)

common/Kconfig | 11 +++++++++++ common/cyclic.c | 27 +++++++++++++++++++++++++-- include/asm-generic/global_data.h | 1 + 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/common/Kconfig b/common/Kconfig index 973482f07566..7a94883f312f 100644 --- a/common/Kconfig +++ b/common/Kconfig @@ -601,6 +601,17 @@ config CYCLIC_MAX_CPU_TIME_US takes longer than this duration this function will get unregistered automatically.

+config CYCLIC_RATELIMIT_US + int "Sets the min time/delay in us after a new call into schedule is done" + default 100 + help + The min allowed time after with a new call into the cyclic + infrastructure is allowed. This results in a rate limiting of the + all functions hooked into the cyclic interface. + As it's been noticed that on some platforms, that high frequent + calls to schedule() (replaced from WATCHDOG_RESET) may lead to a + performance degradation. + endif # CYCLIC

config EVENT diff --git a/common/cyclic.c b/common/cyclic.c index a49bfc88f5c0..9b85afc3c095 100644 --- a/common/cyclic.c +++ b/common/cyclic.c @@ -12,6 +12,7 @@ #include <log.h> #include <malloc.h> #include <time.h> +#include <linux/bug.h> #include <linux/errno.h> #include <linux/list.h> #include <asm/global_data.h> @@ -109,8 +110,30 @@ void schedule(void) * schedule() might get called very early before the cyclic IF is * ready. Make sure to only call cyclic_run() when it's initalized. */ - if (gd) - cyclic_run(); + if (gd) { + uint64_t now; + + /* + * Add some rate limiting to not call into the cyclic IF too + * ofter. As it's been noticed that on some platforms, that + * high frequent calls to schedule() (replaced from + * WATCHDOG_RESET) may lead to a performance degradation. + * -> Do not reset the watchdog too often + */ + now = timer_get_us(); + if (time_after_eq64(now, gd->cyclic_next_call)) { + cyclic_run(); + gd->cyclic_next_call = now + CONFIG_CYCLIC_RATELIMIT_US; + } else { + /* + * Throw a warning (only once) to help identifying + * frantic callers + */ + WARN_ONCE(1, "schedule() called very often, now = %lld us next call at %lld us, dt = %lld us\n", + now, gd->cyclic_next_call, + gd->cyclic_next_call - now); + } + } }

int cyclic_unregister_all(void) diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h index 8fc205ded1a3..0988403d142c 100644 --- a/include/asm-generic/global_data.h +++ b/include/asm-generic/global_data.h @@ -490,6 +490,7 @@ struct global_data { * @cyclic_list: list of registered cyclic functions */ struct hlist_head cyclic_list; + uint64_t cyclic_next_call; #endif /** * @dmtag_list: List of DM tags