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 22:52:48 +0200 [thread overview]
Message-ID: <20180823205248.GA22452@techadventures.net> (raw)
In-Reply-To: <20180823191729.GQ29735@dhcp22.suse.cz>
On Thu, Aug 23, 2018 at 09:17:29PM +0200, Michal Hocko wrote:
> And how exactly does it help to check for the smaller vs. a larger number?
> Both are O(1) operations AFAICS. __highest_present_section_nr makes
> perfect sense when we iterate over all sections or similar operations
> where it smaller number of iterations really makes sense.
Sure, improvement/optimization was not really my point, a comparasion is
a comparasion.
The gain, if any, would be because we would catch
non present sections sooner before calling to present_section().
In the case that __highest_present_section_nr differs from
NR_MEM_SECTIONS, of course.
I thought it would make more sense given the nature of the function itself.
The only thing I did not like much was that we need to export the symbol, though.
So, as you said, the price might be too hight for what we get.
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2018-08-23 20:52 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
2018-08-23 19:17 ` Michal Hocko
2018-08-23 20:52 ` Oscar Salvador [this message]
2018-08-24 0:15 ` Dave Hansen
2018-08-24 18:11 ` Wei Yang
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