The patch titled
Subject: nohz: fix idle ticks in cpu summary line of /proc/stat
has been removed from the -mm tree. Its filename was
nohz-fix-idle-ticks-in-cpu-summary-line-of-proc-stat.patch
This patch was dropped because an updated version will be merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxx>
Subject: nohz: fix idle ticks in cpu summary line of /proc/stat
Commit 09a1d34f8535ecf9 ("nohz: Make idle/iowait counter update
conditional") introduced a bug in regard to cpu hotplug. The effect is
that the number of idle ticks in the cpu summary line in /proc/stat is
still counting ticks for offline cpus.
Reproduction is easy, just start a workload that keeps all cpus busy,
switch off one or more cpus and then watch the idle field in top. On a
dual-core with one cpu 100% busy and one offline cpu you will get
something like this:
%Cpu(s): 48.7 us, 1.3 sy, 0.0 ni, 50.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
The problem is that an offline cpu still has ts->idle_active == 1. To fix
this we should make sure that the cpu is online when calling
get_cpu_idle_time_us and get_cpu_iowait_time_us.
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Reported-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.2.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/stat.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff -puN fs/proc/stat.c~nohz-fix-idle-ticks-in-cpu-summary-line-of-proc-stat fs/proc/stat.c
--- a/fs/proc/stat.c~nohz-fix-idle-ticks-in-cpu-summary-line-of-proc-stat
+++ a/fs/proc/stat.c
@@ -24,10 +24,13 @@
static u64 get_idle_time(int cpu)
{
- u64 idle, idle_time = get_cpu_idle_time_us(cpu, NULL);
+ u64 idle, idle_time = -1ULL;
+
+ if (cpu_online(cpu))
+ idle_time = get_cpu_idle_time_us(cpu, NULL);
if (idle_time == -1ULL) {
- /* !NO_HZ so we can rely on cpustat.idle */
+ /* !NO_HZ or cpu offline so we can rely on cpustat.idle */
idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
idle += arch_idle_time(cpu);
} else
@@ -38,10 +41,13 @@ static u64 get_idle_time(int cpu)
static u64 get_iowait_time(int cpu)
{
- u64 iowait, iowait_time = get_cpu_iowait_time_us(cpu, NULL);
+ u64 iowait, iowait_time = -1ULL;
+
+ if (cpu_online(cpu))
+ iowait_time = get_cpu_iowait_time_us(cpu, NULL);
if (iowait_time == -1ULL)
- /* !NO_HZ so we can rely on cpustat.iowait */
+ /* !NO_HZ or cpu offline so we can rely on cpustat.iowait */
iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
else
iowait = usecs_to_cputime64(iowait_time);
_
Patches currently in -mm which might be from mhocko@xxxxxxx are
origin.patch
memcg-fix-change-behavior-of-shared-anon-at-moving-task.patch
memcg-swap-mem_cgroup_move_swap_account-never-needs-fixup.patch
memcg-swap-use-mem_cgroup_uncharge_swap.patch
mm-memcg-scanning_global_lru-means-mem_cgroup_disabled.patch
mm-memcg-move-reclaim_stat-into-lruvec.patch
mm-push-lru-index-into-shrink_active_list.patch
mm-push-lru-index-into-shrink_active_list-fix.patch
mm-mark-mm-inline-functions-as-__always_inline.patch
mm-remove-lru-type-checks-from-__isolate_lru_page.patch
mm-memcg-kill-mem_cgroup_lru_del.patch
mm-memcg-use-vm_swappiness-from-target-memory-cgroup.patch
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