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From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Waiman Long <longman@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Kees Cook <keescook@chromium.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>,
	Marc Zyngier <marc.zyngier@arm.com>
Subject: Re: [patch V2 1/2] genriq: Avoid summation loops for /proc/stat
Date: Fri, 8 Feb 2019 19:41:17 -0800
Message-ID: <20190209034117.GC21860@bombadil.infradead.org> (raw)
In-Reply-To: <20190208152151.ed4cf0c52e5970fc7a7911f1@linux-foundation.org>

On Fri, Feb 08, 2019 at 03:21:51PM -0800, Andrew Morton wrote:
> It sounds like it.  A 10khz interrupt will overflow in 4 days...

If you've got a 10kHz interrupt, you have a bigger problem.  Anything
happening 10,000 times a second is going to need interrupt mitigation
to perform acceptably.

More importantly, userspace can (and must) cope with wrapping.  This isn't
anything new from Thomas' patch.  As long as userspace is polling more
often than once a day, it's going to see a wrapped value before it wraps
again, so it won't miss 4 billion interrupts.

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 13:48 [patch V2 0/2] genirq, proc: Speedup /proc/stat interrupt statistics Thomas Gleixner
2019-02-08 13:48 ` [patch V2 1/2] genriq: Avoid summation loops for /proc/stat Thomas Gleixner
2019-02-08 22:32   ` Andrew Morton
2019-02-08 22:46     ` Waiman Long
2019-02-08 23:21       ` Andrew Morton
2019-02-09  3:41         ` Matthew Wilcox [this message]
2019-02-13 15:55           ` David Laight
2019-02-08 13:48 ` [patch V2 2/2] proc/stat: Make the interrupt statistics more efficient Thomas Gleixner
2019-02-08 17:01   ` Alexey Dobriyan
2019-02-08 15:20 ` [patch V2 0/2] genirq, proc: Speedup /proc/stat interrupt statistics Waiman Long
2019-02-08 17:01 ` Davidlohr Bueso
2019-02-08 17:40 ` Marc Zyngier

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