linux-kernel - Re: [patch 0/2] genirq, proc: Speedup /proc/stat interrupt statistics

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Message-ID: <alpine.DEB.2.21.1901302300270.8200@nanos.tec.linutronix.de>
Date:   Wed, 30 Jan 2019 23:00:56 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Waiman Long <longman@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Kees Cook <keescook@...omium.org>,
        linux-fsdevel@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
        Miklos Szeredi <miklos@...redi.hu>,
        Daniel Colascione <dancol@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [patch 0/2] genirq, proc: Speedup /proc/stat interrupt
 statistics

On Wed, 30 Jan 2019, Andrew Morton wrote:
> On Wed, 30 Jan 2019 13:31:30 +0100 Thomas Gleixner <tglx@...utronix.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?

Waiman should be able to provide numbers