linux-kernel - Re: [patch 3/6] mempolicy: add MPOL_F_STATIC

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Message-ID: <alpine.DEB.1.00.0802252248400.9390@chino.kir.corp.google.com>
Date:	Mon, 25 Feb 2008 22:53:41 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Paul Jackson <pj@....com>
cc:	akpm@...ux-foundation.org, clameter@....com,
	Lee.Schermerhorn@...com, ak@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/6] mempolicy: add MPOL_F_STATIC_NODES flag

On Mon, 25 Feb 2008, Paul Jackson wrote:

>     $ grep mpol_store_user_nodemask mm/mempolicy.c
>     static inline int mpol_store_user_nodemask(const struct mempolicy *pol)
>         if (mpol_store_user_nodemask(policy))
>         if (!mpol_store_user_nodemask(a))
>         if (!mpol_store_user_nodemask(pol) &&
> 
> So I see no need to waste the instructions needed (in the three copies
> of this code, since it's static inline) to convert a non-zero value to
> exactly the value 1.
> 

Done, thanks.

> Hmmm ... speaking of static inline ... I can knock 600 bytes (that's
> IA64 bytes, so equivalent to about 300 x86 bytes) off the kernel text
> size by not inlining the mm/mempolicy.c routines check_pgd_range() and
> interleave_nid().  I wonder if that would be worth doing.  Perhaps
> those two routines are in sufficiently tight corners that the duplicate
> copies of them is needed.
> 

It seems like a worthwhile change to me even though gcc will pass the 
actuals to check_pgd_range() on the stack.  The callers to check_range() 
shouldn't be in any fast paths: migrate_to_node() can take a long time 
depending on the length of the page list and do_mbind() sleeps on 
mmap_sem.

   text	   data	    bss	    dec	    hex	filename
  11695	     24	     24	  11743	   2ddf	mm/mempolicy.o.before
  11215	     24	     24	  11263	   2bff	mm/mempolicy.o.after
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