From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
alan@lxorguk.ukuu.org.uk,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Michal Hocko <mhocko@suse.cz>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
deepthi@linux.vnet.ibm.com
Subject: [ 03/42] nohz: Fix idle ticks in cpu summary line of /proc/stat
Date: Thu, 25 Oct 2012 17:05:11 -0700 [thread overview]
Message-ID: <20121026000125.142547174@linuxfoundation.org> (raw)
In-Reply-To: <20121026000124.790781113@linuxfoundation.org>
3.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michal Hocko <mhocko@suse.cz>
commit 7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f upstream.
Git 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.
[Srivatsa: Rebased to current mainline]
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20121010061820.8999.57245.stgit@srivatsabhat.in.ibm.com
Cc: deepthi@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/proc/stat.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -45,10 +45,13 @@ static cputime64_t get_iowait_time(int c
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];
else
idle = usecs_to_cputime64(idle_time);
@@ -58,10 +61,13 @@ 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);
next prev parent reply other threads:[~2012-10-26 0:05 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 0:05 [ 00/42] 3.4.16-stable review Greg Kroah-Hartman
2012-10-26 0:05 ` [ 01/42] ext4: race-condition protection for ext4_convert_unwritten_extents_endio Greg Kroah-Hartman
2012-10-26 0:05 ` [ 02/42] ext4: Avoid underflow in ext4_trim_fs() Greg Kroah-Hartman
2012-10-26 0:05 ` Greg Kroah-Hartman [this message]
2012-10-26 0:05 ` [ 04/42] arch/tile: avoid generating .eh_frame information in modules Greg Kroah-Hartman
2012-10-26 0:05 ` [ 05/42] NLM: nlm_lookup_file() may return NLMv4-specific error codes Greg Kroah-Hartman
2012-10-26 0:05 ` [ 06/42] oprofile, x86: Fix wrapping bug in op_x86_get_ctrl() Greg Kroah-Hartman
2012-10-26 0:05 ` [ 07/42] s390: fix linker script for 31 bit builds Greg Kroah-Hartman
2012-10-26 0:05 ` [ 08/42] SUNRPC: Prevent kernel stack corruption on long values of flush Greg Kroah-Hartman
2012-10-26 0:05 ` [ 09/42] SUNRPC: Fix a UDP transport regression Greg Kroah-Hartman
2012-10-26 0:05 ` [ 10/42] pcmcia: sharpsl: dont discard sharpsl_pcmcia_ops Greg Kroah-Hartman
2012-10-26 0:05 ` [ 11/42] kernel/sys.c: fix stack memory content leak via UNAME26 Greg Kroah-Hartman
2012-10-26 0:05 ` [ 13/42] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping Greg Kroah-Hartman
2012-10-26 0:05 ` [ 14/42] xen/x86: dont corrupt %eip when returning from a signal handler Greg Kroah-Hartman
2012-10-26 0:05 ` [ 15/42] USB: cdc-acm: fix pipe type of write endpoint Greg Kroah-Hartman
2012-10-26 0:05 ` [ 16/42] usb: acm: fix the computation of the number of data bits Greg Kroah-Hartman
2012-10-26 0:05 ` [ 17/42] usb: host: xhci: New system added for Compliance Mode Patch on SN65LVPE502CP Greg Kroah-Hartman
2012-10-26 0:05 ` [ 18/42] USB: option: blacklist net interface on ZTE devices Greg Kroah-Hartman
2012-10-26 0:05 ` [ 19/42] USB: option: add more " Greg Kroah-Hartman
2012-10-26 0:05 ` [ 20/42] cgroup: notify_on_release may not be triggered in some cases Greg Kroah-Hartman
2012-10-26 0:05 ` [ 21/42] Revert "cgroup: Remove task_lock() from cgroup_post_fork()" Greg Kroah-Hartman
2012-10-26 0:05 ` [ 22/42] Revert "cgroup: Drop task_lock(parent) on cgroup_fork()" Greg Kroah-Hartman
2012-10-26 0:05 ` [ 23/42] pinctrl: tegra: correct bank for pingroup and drv pingroup Greg Kroah-Hartman
2012-10-26 0:05 ` [ 24/42] pinctrl: tegra: set low power mode bank width to 2 Greg Kroah-Hartman
2012-10-26 0:05 ` [ 25/42] iommu/tegra: smmu: Fix deadly typo Greg Kroah-Hartman
2012-10-26 0:05 ` [ 26/42] amd64_edac:__amd64_set_scrub_rate(): avoid overindexing scrubrates[] Greg Kroah-Hartman
2012-10-26 0:05 ` [ 27/42] usb: dwc3: gadget: fix endpoint always busy bug Greg Kroah-Hartman
2012-10-26 0:05 ` [ 28/42] media: au0828: fix case where STREAMOFF being called on stopped stream causes BUG() Greg Kroah-Hartman
2012-10-26 0:05 ` [ 29/42] netlink: add reference of module in netlink_dump_start Greg Kroah-Hartman
2012-10-26 0:05 ` [ 30/42] infiniband: pass rdma_cm module to netlink_dump_start Greg Kroah-Hartman
2012-10-26 0:05 ` [ 31/42] net: Fix skb_under_panic oops in neigh_resolve_output Greg Kroah-Hartman
2012-10-26 0:05 ` [ 32/42] skge: Add DMA mask quirk for Marvell 88E8001 on ASUS P5NSLI motherboard Greg Kroah-Hartman
2012-10-26 0:05 ` [ 33/42] vlan: dont deliver frames for unknown vlans to protocols Greg Kroah-Hartman
2012-10-26 0:05 ` [ 34/42] RDS: fix rds-ping spinlock recursion Greg Kroah-Hartman
2012-10-26 0:05 ` [ 35/42] tcp: resets are misrouted Greg Kroah-Hartman
2012-10-26 0:05 ` [ 36/42] ipv6: addrconf: fix /proc/net/if_inet6 Greg Kroah-Hartman
2012-10-26 0:05 ` [ 37/42] sparc64: fix ptrace interaction with force_successful_syscall_return() Greg Kroah-Hartman
2012-10-26 0:05 ` [ 38/42] sparc64: Like x86 we should check current->mm during perf backtrace generation Greg Kroah-Hartman
2012-10-26 0:05 ` [ 39/42] sparc64: Fix bit twiddling in sparc_pmu_enable_event() Greg Kroah-Hartman
2012-10-26 0:05 ` [ 40/42] sparc64: do not clobber personality flags in sys_sparc64_personality() Greg Kroah-Hartman
2012-10-26 0:05 ` [ 41/42] sparc64: Be less verbose during vmemmap population Greg Kroah-Hartman
2012-10-26 0:05 ` [ 42/42] mtd: nand: allow NAND_NO_SUBPAGE_WRITE to be set from driver Greg Kroah-Hartman
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