linux-kernel - Re: [PATCH 4/7] kref: Remove WARN

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Message-ID: <20170315122731.GR3093@worktop>
Date:   Wed, 15 Mar 2017 13:27:31 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 4/7] kref: Remove WARN_ON for NULL release functions

On Wed, Mar 15, 2017 at 10:46:56AM +0800, Greg KH wrote:
> On Tue, Mar 14, 2017 at 07:14:28PM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > The kref functions check for NULL release functions.
> > This WARN_ON seems rather pointless. We will eventually release and
> > then just crash nicely. It is also somewhat expensive because
> > these functions are inlined in a lot of places.
> > Removing the WARN_ONs saves around 2.3k in this kernel
> > (likely more in others with more drivers)
> > 
> >    text    data     bss     dec     hex filename
> > 9083992 5367600 11116544        25568136        1862388 vmlinux-before-load-avg
> > 9070166 5367600 11116544        25554310        185ed86 vmlinux-load-avg
> 
> WARN_ON() is heavy, didn't realize that.

I actually have patches fixing that.