From: Matthew Wilcox <willy@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Miklos Szeredi <miklos@szeredi.hu>,
Daniel Colascione <dancol@google.com>,
Dave Chinner <david@fromorbit.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v3 4/4] /proc/stat: Call kstat_irqs_usr() only for active IRQs
Date: Fri, 11 Jan 2019 11:23:58 -0800 [thread overview]
Message-ID: <20190111192357.GK6310@bombadil.infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1901112017000.1661@nanos.tec.linutronix.de>
On Fri, Jan 11, 2019 at 08:19:33PM +0100, Thomas Gleixner wrote:
> On Fri, 11 Jan 2019, Thomas Gleixner wrote:
> > --- a/kernel/irq/internals.h
> > +++ b/kernel/irq/internals.h
> > @@ -246,6 +246,7 @@ static inline void kstat_incr_irqs_this_
> > {
> > __this_cpu_inc(*desc->kstat_irqs);
> > __this_cpu_inc(kstat.irqs_sum);
> > + desc->tot_count++;
>
> There is one issue here. True percpu interrupts, like the timer interrupts
> on ARM(64), will access that in parallel. But that's not rocket science to
> fix.
I was wondering about that from an efficiency point of view. Since
interrupts are generally targetted to a single CPU, there's no cacheline
bouncing to speak of, except for interrupts like TLB shootdown on x86.
It might make sense for the percpu interrupts to still sum them at read
time, and not sum them at interrupt time.
next prev parent reply other threads:[~2019-01-11 19:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 19:20 [PATCH v3 0/4] /proc/stat: Reduce irqs counting performance overhead Waiman Long
2019-01-09 19:20 ` [PATCH v3 1/4] /proc/stat: Extract irqs counting code into show_stat_irqs() Waiman Long
2019-01-09 19:20 ` [PATCH v3 2/4] /proc/stat: Only do percpu sum of active IRQs Waiman Long
2019-01-09 19:20 ` [PATCH v3 3/4] genirq: Track the number " Waiman Long
2019-01-09 19:20 ` Waiman Long
2019-01-09 19:20 ` [PATCH v3 4/4] /proc/stat: Call kstat_irqs_usr() only for " Waiman Long
2019-01-11 17:23 ` Thomas Gleixner
2019-01-11 17:23 ` Thomas Gleixner
2019-01-11 19:19 ` Thomas Gleixner
2019-01-11 19:19 ` Thomas Gleixner
2019-01-11 19:23 ` Matthew Wilcox [this message]
2019-01-11 19:23 ` Matthew Wilcox
2019-01-11 21:02 ` Thomas Gleixner
2019-01-11 21:02 ` Thomas Gleixner
2019-01-14 19:04 ` Waiman Long
2019-01-14 19:04 ` Waiman Long
2019-01-15 9:24 ` Thomas Gleixner
2019-01-15 9:24 ` Thomas Gleixner
2019-01-15 15:52 ` Waiman Long
2019-01-15 15:52 ` Waiman Long
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