From: Oscar Salvador <osalvador@techadventures.net>
To: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@gmail.com>,
akpm@linux-foundation.org, rientjes@google.com,
linux-mm@kvack.org, kirill.shutemov@linux.intel.com,
bob.picco@hp.com
Subject: Re: [PATCH 3/3] mm/sparse: use __highest_present_section_nr as the boundary for pfn check
Date: Thu, 23 Aug 2018 16:00:53 +0200 [thread overview]
Message-ID: <20180823140053.GC14924@techadventures.net> (raw)
In-Reply-To: <20180823132526.GL29735@dhcp22.suse.cz>
On Thu, Aug 23, 2018 at 03:25:26PM +0200, Michal Hocko wrote:
> On Thu 23-08-18 21:07:32, Wei Yang wrote:
> > And it is known, __highest_present_section_nr is a more strict boundary
> > than NR_MEM_SECTIONS.
> >
> > This patch uses a __highest_present_section_nr to check a valid pfn.
>
> But why is this an improvement? Sure when you loop over all sections
> than __highest_present_section_nr makes a lot of sense. But all the
> updated function perform a trivial comparision.
I think it makes some sense.
NR_MEM_SECTIONS can be a big number, but we might not be using
all sections, so __highest_present_section_nr ends up being a much lower
value.
I think that we want to compare the pfn's section_nr with our current limit
of present sections.
Sections over that do not really exist for us, so it is no use to look for
them in __nr_to_section/valid_section.
It might not be a big improvement, but I think that given the nature of
pfn_valid/pfn_present, comparing to __highest_present_section_nr suits better.
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2018-08-23 14:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 13:07 [PATCH 0/3] trivial code refine for sparsemem Wei Yang
2018-08-23 13:07 ` [PATCH 1/3] mm/sparse: add likely to mem_section[root] check in sparse_index_init() Wei Yang
2018-08-23 13:13 ` Michal Hocko
2018-08-23 22:57 ` Wei Yang
2018-08-24 7:31 ` Michal Hocko
2018-08-24 0:11 ` Dave Hansen
2018-08-24 15:07 ` Wei Yang
2018-09-03 22:27 ` Wei Yang
2018-09-09 1:38 ` Wei Yang
2018-09-10 20:30 ` Dave Hansen
2018-09-11 15:00 ` Wei Yang
2018-08-23 13:07 ` [PATCH 2/3] mm/sparse: expand the CONFIG_SPARSEMEM_EXTREME range in __nr_to_section() Wei Yang
2018-08-23 13:21 ` Michal Hocko
2018-08-23 23:03 ` Wei Yang
2018-08-24 0:09 ` Dave Hansen
2018-08-24 15:24 ` Wei Yang
2018-08-23 13:07 ` [PATCH 3/3] mm/sparse: use __highest_present_section_nr as the boundary for pfn check Wei Yang
2018-08-23 13:25 ` Michal Hocko
2018-08-23 14:00 ` Oscar Salvador [this message]
2018-08-23 19:17 ` Michal Hocko
2018-08-23 20:52 ` Oscar Salvador
2018-08-24 0:15 ` Dave Hansen
2018-08-24 18:11 ` Wei Yang
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