Michal Hocko 2a95ea6c0d procfs: do not overflow get_{idle,iowait}_time for nohz ... Since commit a25cac5198 ("proc: Consider NO_HZ when printing idle and iowait times") we are reporting idle/io_wait time also while a CPU is tickless. We rely on get_{idle,iowait}_time functions to retrieve proper data. These functions, however, use usecs_to_cputime to translate micro seconds time to cputime64_t. This is just an alias to usecs_to_jiffies which reduces the data type from u64 to unsigned int and also checks whether the given parameter overflows jiffies_to_usecs(MAX_JIFFY_OFFSET) and returns MAX_JIFFY_OFFSET in that case. When we overflow depends on CONFIG_HZ but especially for CONFIG_HZ_300 it is quite low (1431649781) so we are getting MAX_JIFFY_OFFSET for >3000s! until we overflow unsigned int. Just for reference CONFIG_HZ_100 has an overflow window around 20s, CONFIG_HZ_250 ~8s and CONFIG_HZ_1000 ~2s. This results in a bug when people saw [h]top going mad reporting 100% CPU usage even though there was basically no CPU load. The reason was simply that /proc/stat stopped reporting idle/io_wait changes (and reported MAX_JIFFY_OFFSET) and so the only change happening was for user system time. Let's use nsecs_to_jiffies64 instead which doesn't reduce the precision to 32b type and it is much more appropriate for cumulative time values (unlike usecs_to_jiffies which intended for timeout calculations). Signed-off-by: Michal Hocko <mhocko@suse.cz> Tested-by: Artem S. Tashkinov <t.artem@mailcity.com> Cc: Dave Jones <davej@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2011-12-09 07:50:29 -08:00
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array.c
base.c	Revert "proc: fix races against execve() of /proc/PID/fd**"	2011-11-09 18:16:00 -05:00
cmdline.c
consoles.c
cpuinfo.c
devices.c
generic.c	filesystems: add set_nlink()	2011-11-02 12:53:43 +01:00
inode.c	filesystems: add set_nlink()	2011-11-02 12:53:43 +01:00
internal.h
interrupts.c
Kconfig
kcore.c
kmsg.c
loadavg.c
Makefile
meminfo.c	fs/proc/meminfo.c: fix compilation error	2011-12-09 07:50:28 -08:00
mmu.c
namespaces.c
nommu.c
page.c
proc_devtree.c
proc_net.c	proc: make struct proc_dir_entry::name a terminal array rather than a pointer	2011-07-27 12:50:45 -07:00
proc_sysctl.c	Merge branch 'akpm' (Andrew's incoming - part two)	2011-11-02 16:07:27 -07:00
proc_tty.c
root.c	proc: make struct proc_dir_entry::name a terminal array rather than a pointer	2011-07-27 12:50:45 -07:00
softirqs.c
stat.c	procfs: do not overflow get_{idle,iowait}_time for nohz	2011-12-09 07:50:29 -08:00
task_mmu.c	mm: distinguish between mlocked and pinned pages	2011-10-31 17:30:46 -07:00
task_nommu.c
uptime.c
version.c
vmcore.c	fs: add export.h to files using EXPORT_SYMBOL/THIS_MODULE macros	2011-10-31 19:30:31 -04:00