Messages in this thread | | | Date | Wed, 28 Feb 2018 18:02:10 -0500 | From | Theodore Ts'o <> | Subject | Re: [PATCH] random: Optimize add_interrupt_randomness |
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Thanks, applied.
- Ted
On Wed, Feb 28, 2018 at 01:43:28PM -0800, Andi Kleen wrote: > From: Andi Kleen <ak@linux.intel.com> > > add_interrupt_randomess always wakes up > code blocking on /dev/random. This wake up is done > unconditionally. Unfortunately this means all interrupts > take the wait queue spinlock, which can be rather expensive > on large systems processing lots of interrupts. > > We saw 1% cpu time spinning on this on a large macro workload > running on a large system. > > I believe it's a recent regression (?) > > Always check if there is a waiter on the wait queue > before waking up. This check can be done without > taking a spinlock. > > 1.06% 10460 [kernel.vmlinux] [k] native_queued_spin_lock_slowpath > | > ---native_queued_spin_lock_slowpath > | > --0.57%--_raw_spin_lock_irqsave > | > --0.56%--__wake_up_common_lock > credit_entropy_bits > add_interrupt_randomness > handle_irq_event_percpu > handle_irq_event > handle_edge_irq > handle_irq > do_IRQ > common_interrupt > > Signed-off-by: Andi Kleen <ak@linux.intel.com>
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