linux-kernel - Re: [RFC][PATCH 3/6] break out smaps_pte_entry() from smaps_pte

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Date:	Thu, 03 Feb 2011 13:40:23 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael J Wolf <mjwolf@...ibm.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC][PATCH 3/6] break out smaps_pte_entry() from
 smaps_pte_range()

On Thu, 2011-02-03 at 13:22 -0800, David Rientjes wrote:
> On Mon, 31 Jan 2011, Dave Hansen wrote:
> > We will use smaps_pte_entry() in a moment to handle both small
> > and transparent large pages.  But, we must break it out of
> > smaps_pte_range() first.
> 
> The extraction from smaps_pte_range() looks good.  What's the performance 
> impact on very frequent consumers of /proc/pid/smaps, though, as the 
> result of the calls throughout the iteration if smaps_pte_entry() doesn't 
> get inlined (supposedly because you'll be reusing the extracted function 
> again elsewhere)?

We could try and coerce it in to always inlining it, I guess.  I just
can't imagine this changes the cost _that_ much.  Unless I have some
specific concers, I tend to leave this up to the compiler, and none of
the users look particularly fastpathy or performance sensitive to me.

...
> > -	}
> > +	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> > +	for (; addr != end; pte++, addr += PAGE_SIZE)
> > +		smaps_pte_entry(*pte, addr, walk);
> >  	pte_unmap_unlock(pte - 1, ptl);
> >  	cond_resched();
> >  	return 0;
> > diff -puN mm/huge_memory.c~break-out-smaps_pte_entry mm/huge_memory.c
> > _
> 
> Is there a missing change to mm/huge_memory.c?

Nope, it was just more of those empty diffs like in the last patch.
It's cruft from patch-scripts and some code that I use to ensure I don't
miss file edits when making patches.  I'll pull them out.

-- Dave

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