• Rik van Riel's avatar
    sched/cputime: Count actually elapsed irq & softirq time · 57430218
    Rik van Riel authored
    Currently, if there was any irq or softirq time during 'ticks'
    jiffies, the entire period will be accounted as irq or softirq
    time.
    
    This is inaccurate if only a subset of the time was actually spent
    handling irqs, and could conceivably mis-count all of the ticks during
    a period as irq time, when there was some irq and some softirq time.
    
    This can actually happen when irqtime_account_process_tick is called
    from account_idle_ticks, which can pass a larger number of ticks down
    all at once.
    
    Fix this by changing irqtime_account_hi_update(), irqtime_account_si_update(),
    and steal_account_process_ticks() to work with cputime_t time units, and
    return the amount of time spent in each mode.
    
    Rename steal_account_process_ticks() to steal_account_process_time(), to
    reflect that time is now accounted in cputime_t, instead of ticks.
    
    Additionally, have irqtime_account_process_tick() take into account how
    much time was spent in each of steal, irq, and softirq time.
    
    The latter could help improve the accuracy of cputime
    accounting when returning from idle on a NO_HZ_IDLE CPU.
    
    Properly accounting how much time was spent in hardirq and
    softirq time will also allow the NO_HZ_FULL code to re-use
    these same functions for hardirq and softirq accounting.
    Signed-off-by: 's avatarRik van Riel <riel@redhat.com>
    [ Make nsecs_to_cputime64() actually return cputime64_t. ]
    Signed-off-by: 's avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Radim Krcmar <rkrcmar@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Wanpeng Li <wanpeng.li@hotmail.com>
    Link: http://lkml.kernel.org/r/1468421405-20056-2-git-send-email-fweisbec@gmail.comSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
    57430218
cputime_nsecs.h 3.14 KB