linux-kernel - Re: [PATCH v2] kthread: Export kthread functions

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Message-ID: <20150801133221.GA6603@neilslaptop.think-freely.org>
Date:	Sat, 1 Aug 2015 09:32:21 -0400
From:	Neil Horman <nhorman@...hat.com>
To:	yalin wang <yalin.wang2010@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Kershner <david.kershner@...sys.com>, tj@...nel.org,
	laijs@...fujitsu.com, nacc@...ux.vnet.ibm.com, mingo@...hat.com,
	open list <linux-kernel@...r.kernel.org>,
	jes.sorensen@...hat.com, sparmaintainer@...sys.com
Subject: Re: [PATCH v2] kthread: Export kthread functions

On Sat, Aug 01, 2015 at 03:12:42PM +0800, yalin wang wrote:
> 
> > 在 2015年7月31日，22:14，Thomas Gleixner <tglx@...utronix.de> 写道：
> > 
> > 
> > On Fri, 31 Jul 2015, Thomas Gleixner wrote:
> > 
> >> On Fri, 31 Jul 2015, yalin wang wrote:
> >>> it is optimised to 2 instructions ,
> >>> 
> >>> this is my patch, hope can be merged :
> >> 
> >> We are not exposing the internals of kthread management. Period.
> > 
> > And your 'optimization' is completely bogus:
> > 
> > Before your modification:
> > 
> > size kernel/built-in.o
> > 
> >   text	   data	    bss	    dec	    hex	filename
> > 1091514	 141498  341928 1574940  18081c	../build/kernel/built-in.o
> > 
> > After:
> > 
> >   text	   data	    bss	    dec	    hex	filename
> > 1091664  141498  341928 1575090  1808b2	../build/kernel/built-in.o
> > 
> > That's an increase of text size by 150 byte. Interesting optimization.
> > 
> > Thanks,
> > 
> > 	tglx
> > 
> > 
> strange,  this is my test result:
> 
> size   built-in.o*
>   text	   data	    bss	    dec	    hex	filename
> 743937	  50786	  56008	 850731	  cfb2b	built-in.o        // with the patch
> 744069	  50786	  56008	 850863	  cfbaf	built-in.o_old  // with out the patch
> 
So you're willing to expose the internals of kthread_park in exchange for the
hope of saving 132 bytes of text.

Thats just dumb.  I agree with tglx, this shouldn't change.

Neil

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