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authorJosh Don <joshdon@google.com>2021-08-27 19:54:38 +0300
committerPeter Zijlstra <peterz@infradead.org>2021-10-05 16:51:35 +0300
commita130e8fbc7de796eb6e680724d87f4737a26d0ac (patch)
tree4adeb41642500b6aca5ddd2b1144a9785e2e591e /include/linux/kernel_stat.h
parentbc9ffef31bf59819c9fc032178534ff9ed7c4981 (diff)
downloadlinux-a130e8fbc7de796eb6e680724d87f4737a26d0ac.tar.xz
fs/proc/uptime.c: Fix idle time reporting in /proc/uptime
/proc/uptime reports idle time by reading the CPUTIME_IDLE field from the per-cpu kcpustats. However, on NO_HZ systems, idle time is not continually updated on idle cpus, leading this value to appear incorrectly small. /proc/stat performs an accounting update when reading idle time; we can use the same approach for uptime. With this patch, /proc/stat and /proc/uptime now agree on idle time. Additionally, the following shows idle time tick up consistently on an idle machine: (while true; do cat /proc/uptime; sleep 1; done) | awk '{print $2-prev; prev=$2}' Reported-by: Luigi Rizzo <lrizzo@google.com> Signed-off-by: Josh Don <joshdon@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lkml.kernel.org/r/20210827165438.3280779-1-joshdon@google.com
Diffstat (limited to 'include/linux/kernel_stat.h')
-rw-r--r--include/linux/kernel_stat.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 44ae1a7eb9e3..69ae6b278464 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -102,6 +102,7 @@ extern void account_system_index_time(struct task_struct *, u64,
enum cpu_usage_stat);
extern void account_steal_time(u64);
extern void account_idle_time(u64);
+extern u64 get_idle_time(struct kernel_cpustat *kcs, int cpu);
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
static inline void account_process_tick(struct task_struct *tsk, int user)