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Date:   Wed, 30 Jan 2019 13:58:45 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Waiman Long <longman@redhat.com>,
        Matthew Wilcox <willy@infradead.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 0/2] genirq, proc: Speedup /proc/stat interrupt
 statistics
Message-Id: <20190130135845.406c51b7f565232a7fed0de6@linux-foundation.org>
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References: <20190130123130.785636313@linutronix.de>
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On Wed, 30 Jan 2019 13:31:30 +0100 Thomas Gleixner <tglx@linutronix.de> 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.
> 
> The following series addresses this by making the interrupt statitics code
> in the core generate the sum directly and by making the loop in the
> /proc/stat read function smarter.
> 

Has the speedup been quantified?