On 01/30/2019 07:31 AM, Thomas Gleixner wrote: > Waiman reported that on large systems with a large amount of interrupts the > readout of /proc/stat takes a long time to sum up the interrupt > statistics. In principle this is not a problem. but for unknown reasons > some enterprise quality software reads /proc/stat with a high frequency. > > The reason for this is that interrupt statistics are accounted per cpu. So > the /proc/stat logic has to sum up the interrupt stats for each interrupt. > > This can be largely avoided for interrupts which are not marked as > 'PER_CPU' interrupts by simply adding a per interrupt summation counter > which is incremented along with the per interrupt per cpu counter. > > The PER_CPU interrupts need to avoid that and use only per cpu accounting > because they share the interrupt number and the interrupt descriptor and > concurrent updates would conflict or require unwanted synchronization. > > Reported-by: Waiman Long <[email protected]> > Signed-off-by: Thomas Gleixner <[email protected]> > > 8<------------- > > include/linux/irqdesc.h | 3 ++- > kernel/irq/chip.c | 12 ++++++++++-- > kernel/irq/internals.h | 8 +++++++- > kernel/irq/irqdesc.c | 7 ++++++- > 4 files changed, 25 insertions(+), 5 deletions(-) > > > --- a/include/linux/irqdesc.h > +++ b/include/linux/irqdesc.h > @@ -65,9 +65,10 @@ struct irq_desc { > unsigned int core_internal_state__do_not_mess_with_it; > unsigned int depth; /* nested irq disables */ > unsigned int wake_depth; /* nested wake enables */ > + unsigned int tot_count; > unsigned int irq_count; /* For detecting broken IRQs */ > - unsigned long last_unhandled; /* Aging timer for unhandled > count */ > unsigned int irqs_unhandled; > + unsigned long last_unhandled; /* Aging timer for unhandled > count */ > atomic_t threads_handled; > int threads_handled_last; > raw_spinlock_t lock;
Just one minor nit. Why you want to move the last_unhandled down one slot? There were 5 int's before. Adding one more will just fill the padding hole. Moving down the last_unhandled will probably leave 4-byte holes in both above and below it assuming that raw_spinlock_t is 4 bytes. Cheers, Longman
