Messages in this thread Patch in this message | | | From | Song Liu <> | Subject | [PATCH v4] watchdog: Allow nmi watchdog to use "ref-cycles" event | Date | Wed, 17 May 2023 17:25:55 -0700 |
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NMI watchdog permanently consumes one hardware counters per CPU on the system. For systems that use many hardware counters, this causes more aggressive time multiplexing of perf events.
OTOH, some CPUs (mostly Intel) support "ref-cycles" event, which is rarely used. Add kernel cmdline arg nmi_watchdog=ref-cycles to configure the watchdog to use "ref-cycles" event instead of "cycles".
Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Song Liu <song@kernel.org>
--- Changes in v4: Fix compile error for !CONFIG_HARDLOCKUP_DETECTOR_PERF. (kernel test bot)
Changes in v3:
Pivot the design to use kernel arg nmi_watchdog=ref-cycles (Peter) --- Documentation/admin-guide/kernel-parameters.txt | 5 +++-- include/linux/nmi.h | 2 ++ kernel/watchdog.c | 2 ++ kernel/watchdog_hld.c | 9 +++++++++ 4 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9e5bab29685f..d378e23dad7c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3593,10 +3593,12 @@ Format: [state][,regs][,debounce][,die] nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels - Format: [panic,][nopanic,][num] + Format: [panic,][nopanic,][ref-cycles][num] Valid num: 0 or 1 0 - turn hardlockup detector in nmi_watchdog off 1 - turn hardlockup detector in nmi_watchdog on + ref-cycles - configure the watchdog with perf event + "ref-cycles" instead of "cycles" When panic is specified, panic when an NMI watchdog timeout occurs (or 'nopanic' to not panic on an NMI watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) @@ -7097,4 +7099,3 @@ memory, and other data can't be written using xmon commands. off xmon is disabled. - diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 048c0b9aa623..edfd1bcce0f6 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -102,12 +102,14 @@ extern void hardlockup_detector_perf_disable(void); extern void hardlockup_detector_perf_enable(void); extern void hardlockup_detector_perf_cleanup(void); extern int hardlockup_detector_perf_init(void); +extern void hardlockup_config_perf_event(const char *str); #else static inline void hardlockup_detector_perf_stop(void) { } static inline void hardlockup_detector_perf_restart(void) { } static inline void hardlockup_detector_perf_disable(void) { } static inline void hardlockup_detector_perf_enable(void) { } static inline void hardlockup_detector_perf_cleanup(void) { } +static inline void hardlockup_config_perf_event(const char *str) { } # if !defined(CONFIG_HAVE_NMI_WATCHDOG) static inline int hardlockup_detector_perf_init(void) { return -ENODEV; } static inline void arch_touch_nmi_watchdog(void) {} diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 8e61f21e7e33..fed4f0be8e1a 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -81,6 +81,8 @@ static int __init hardlockup_panic_setup(char *str) nmi_watchdog_user_enabled = 0; else if (!strncmp(str, "1", 1)) nmi_watchdog_user_enabled = 1; + else if (!strncmp(str, "ref-cycles", 10)) + hardlockup_config_perf_event(str); return 1; } __setup("nmi_watchdog=", hardlockup_panic_setup); diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index 247bf0b1582c..4deca58ba6ed 100644 --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -294,3 +294,12 @@ int __init hardlockup_detector_perf_init(void) } return ret; } + +/** + * hardlockup_config_perf_event - Overwrite config of wd_hw_attr + */ +void __init hardlockup_config_perf_event(const char *str) +{ + if (!strncmp(str, "ref-cycles", 10)) + wd_hw_attr.config = PERF_COUNT_HW_REF_CPU_CYCLES; +} -- 2.34.1
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