linux-kernel - Re: [patch V2 0/2] genirq, proc: Speedup /proc/stat interrupt statistics

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Message-ID: <20190208170137.7w63kmg56ltjomsj@linux-r8p5>
Date:   Fri, 8 Feb 2019 09:01:37 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Waiman Long <longman@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Kees Cook <keescook@...omium.org>,
        linux-fsdevel@...r.kernel.org, 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 V2 0/2] genirq, proc: Speedup /proc/stat interrupt
 statistics

On Fri, 08 Feb 2019, Thomas Gleixner 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.
>
>V1 -> V2: Address review feedback: undo struct layout changes, make
>      	  variables unsigned and add test results to the changelog.
>
>Thanks,
>
>        tglx
>
>8<----------------
> fs/proc/stat.c          |   29 ++++++++++++++++++++++++++---
> include/linux/irqdesc.h |    1 +
> kernel/irq/chip.c       |   12 ++++++++++--
> kernel/irq/internals.h  |    8 +++++++-
> kernel/irq/irqdesc.c    |    7 ++++++-
> 5 files changed, 50 insertions(+), 7 deletions(-)

Reviewed-by: Davidlohr Bueso <dbueso@...e.de>