lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 9 Jan 2019 13:03:33 -0500
From:   Waiman Long <longman@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...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 v2 0/4] /proc/stat: Reduce irqs counting performance
 overhead

On 01/09/2019 12:44 PM, Matthew Wilcox wrote:
> On Wed, Jan 09, 2019 at 12:23:44PM -0500, Waiman Long wrote:
>> This v2 patch optimizes the way the IRQ counts are retrieved and computed
>> and getting rid of the sysctl parameter altogether to achieve a performance
>> gain that is close to the v1 patch. This is based on the idea that while
>> many IRQs can be supported by a system, only a handful of them are actually
>> being used in most cases. We can save a lot of time by focusing on those
>> active IRQs only and ignore the rests.
> So your reaction to being told "Make this the same as every other thing
> we have to sum across all CPUs" is to make it _even more different_ and
> special-cased?  I'm done.  NAK.

The paragraph above may be a bit misleading. This v2 patch actually
touches very little on percpu accounting aspect of the IRQ counts. See
patches 2 and 3 for the relevant changes which is just a few line of new
codes. Please review the individual patches before Nak'ing.

I could theoretically generalize them into a new set of percpu counting
helpers, but the idea behind it is quite different from the use cases of
percpu counter. So it may not be a good idea of adding it to there.

Cheers,
Longman


Powered by blists - more mailing lists