Date: Mon, 28 Feb 2005 20:41:31 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Mauricio Lin <mauriciolin@gmail.com>
cc: Andrew Morton <akpm@osdl.org>, wli@holomorphy.com,
       linux-kernel@vger.kernel.org, rrebel@whenu.com,
       marcelo.tosatti@cyclades.com, nickpiggin@yahoo.com.au
Subject: Re: [PATCH] A new entry for /proc
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On Mon, 28 Feb 2005, Mauricio Lin wrote:
> 
> Now I am testing with /proc/pid/smaps and the values are showing that
> the old one is faster than the new one. So I will keep using the old
> smaps version.

Sorry, I don't have time for more than the briefest look.

It appears that your old resident_mem_size method is just checking
pte_present, whereas your new smaps_pte_range method is also doing
pte_page (yet no prior check for pfn_valid: wrong) and checking
!PageReserved i.e. accessing the struct page corresponding to each
pte.  So it's not a fair comparison, your new method is accessing
many more cachelines than your old method.

Though it's correct to check pfn_valid and !PageReserved to get the
same total rss as would be reported elsewhere, I'd suggest that it's
really not worth the overhead of those struct page accesses: just
stick with the pte_present test.

Your smaps_pte_range is missing pte_unmap?

Hugh
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