linux-kernel - Re: [PATCH 2/2] /proc/stat: Add sysctl parameter to control irq counts latency

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Date:   Mon, 7 Jan 2019 19:33:01 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.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>
Subject: Re: [PATCH 2/2] /proc/stat: Add sysctl parameter to control irq
 counts latency

On Mon, Jan 07, 2019 at 07:58:40AM -0800, Matthew Wilcox wrote:
> On Mon, Jan 07, 2019 at 10:12:58AM -0500, Waiman Long wrote:

> > A new "fs/proc-stat-irqs-latency-ms" sysctl parameter is now added to
> 
> No.  No, no, no, no, no.  No.
> 
> Stop adding new sysctls for this kind of thing.  It's just a way to shift
> blame from us (who allegedly know what we're doing) to the sysadmin
> (who probably has better things to be doing than keeping up with the
> intricacies of development of every single piece of software running on
> their system).
> 
> Let's figure out what this _should_ be.

Yeah, let's start interrogating about which values specifically this
super sekret applications wants.

I assume CPU stats, so system call which returns CPU statistics in binary form.

> Why are you caching the _output_ of calling sprintf(), rather than caching the
> values of each interrupt?

For output caching string is better, but I'm not defending the patch.