• Thomas Gleixner's avatar
    hrtimer: Tune hrtimer_interrupt hang logic · 41d2e494
    Thomas Gleixner authored
    
    
    The hrtimer_interrupt hang logic adjusts min_delta_ns based on the
    execution time of the hrtimer callbacks.
    
    This is error-prone for virtual machines, where a guest vcpu can be
    scheduled out during the execution of the callbacks (and the callbacks
    themselves can do operations that translate to blocking operations in
    the hypervisor), which in can lead to large min_delta_ns rendering the
    system unusable.
    
    Replace the current heuristics with something more reliable. Allow the
    interrupt code to try 3 times to catch up with the lost time. If that
    fails use the total time spent in the interrupt handler to defer the
    next timer interrupt so the system can catch up with other things
    which got delayed. Limit that deferment to 100ms.
    
    The retry events and the maximum time spent in the interrupt handler
    are recorded and exposed via /proc/timer_list
    
    Inspired by a patch from Marcelo.
    Reported-by: default avatarMichael Tokarev <mjt@tls.msk.ru>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Tested-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
    Cc: kvm@vger.kernel.org
    41d2e494
timer_list.c 7.33 KB