From 393fb313a2e150b768e4850658679e2afff431e9 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Mon, 29 Apr 2024 23:02:36 -0700 Subject: watchdog: allow nmi watchdog to use raw perf event 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=rNNN to configure the watchdog to use raw event. For example, on Intel CPUs, we can use "r300" to configure the watchdog to use ref-cycles event. If the raw event does not work, fall back to use "cycles". [akpm@linux-foundation.org: fix kerneldoc] Link: https://lkml.kernel.org/r/20240430060236.1878002-2-song@kernel.org Signed-off-by: Song Liu Cc: Peter Zijlstra Cc: "Matthew Wilcox (Oracle)" Signed-off-by: Andrew Morton --- kernel/watchdog.c | 2 ++ kernel/watchdog_perf.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+) (limited to 'kernel') diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 7f54484de16f..ab0129b15f25 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -80,6 +80,8 @@ next: watchdog_hardlockup_user_enabled = 0; else if (!strncmp(str, "1", 1)) watchdog_hardlockup_user_enabled = 1; + else if (!strncmp(str, "r", 1)) + hardlockup_config_perf_event(str + 1); while (*(str++)) { if (*str == ',') { str++; diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c index 8ea00c4a24b2..5f7d1f0d4268 100644 --- a/kernel/watchdog_perf.c +++ b/kernel/watchdog_perf.c @@ -90,6 +90,14 @@ static struct perf_event_attr wd_hw_attr = { .disabled = 1, }; +static struct perf_event_attr fallback_wd_hw_attr = { + .type = PERF_TYPE_HARDWARE, + .config = PERF_COUNT_HW_CPU_CYCLES, + .size = sizeof(struct perf_event_attr), + .pinned = 1, + .disabled = 1, +}; + /* Callback function for perf event subsystem */ static void watchdog_overflow_callback(struct perf_event *event, struct perf_sample_data *data, @@ -122,6 +130,13 @@ static int hardlockup_detector_event_create(void) /* Try to register using hardware perf events */ evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); + if (IS_ERR(evt)) { + wd_attr = &fallback_wd_hw_attr; + wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); + evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, + watchdog_overflow_callback, NULL); + } + if (IS_ERR(evt)) { pr_debug("Perf event create on CPU %d failed with %ld\n", cpu, PTR_ERR(evt)); @@ -259,3 +274,34 @@ int __init watchdog_hardlockup_probe(void) } return ret; } + +/** + * hardlockup_config_perf_event - Overwrite config of wd_hw_attr. + * + * @str: number which identifies the raw perf event to use + */ +void __init hardlockup_config_perf_event(const char *str) +{ + u64 config; + char buf[24]; + char *comma = strchr(str, ','); + + if (!comma) { + if (kstrtoull(str, 16, &config)) + return; + } else { + unsigned int len = comma - str; + + if (len >= sizeof(buf)) + return; + + if (strscpy(buf, str, sizeof(buf)) < 0) + return; + buf[len] = 0; + if (kstrtoull(buf, 16, &config)) + return; + } + + wd_hw_attr.type = PERF_TYPE_RAW; + wd_hw_attr.config = config; +} -- cgit v1.2.3