From: Michal Hocko <mhocko@suse.com>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: akpm@linux-foundation.org, rientjes@google.com,
linux-mm@kvack.org, kirill.shutemov@linux.intel.com,
bob.picco@hp.com
Subject: Re: [PATCH 1/3] mm/sparse: add likely to mem_section[root] check in sparse_index_init()
Date: Fri, 24 Aug 2018 09:31:08 +0200 [thread overview]
Message-ID: <20180824073108.GX29735@dhcp22.suse.cz> (raw)
In-Reply-To: <20180823225742.bsmci4gxv3dho2ke@master>
On Thu 23-08-18 22:57:42, Wei Yang wrote:
> On Thu, Aug 23, 2018 at 03:13:39PM +0200, Michal Hocko wrote:
> >On Thu 23-08-18 21:07:30, Wei Yang wrote:
> >> Each time SECTIONS_PER_ROOT number of mem_section is allocated when
> >> mem_section[root] is null. This means only (1 / SECTIONS_PER_ROOT) chance
> >> of the mem_section[root] check is false.
> >>
> >> This patch adds likely to the if check to optimize this a little.
> >
> >Could you evaluate how much does this help if any? Does this have any
> >impact on the initialization path at all?
>
> Let me test on my 4G machine with this patch :-)
Well, this should have been done before posting the patch. In general,
though, you should have some convincing numbers in order to add new
likely/unlikely annotations. They are rarely helpful and they tend to
rot over time. Steven Rostedt has made some test few years back and
found out that a vast majority of those annotation were simply wrong.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-08-24 7:31 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 [this message]
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
2018-08-24 0:15 ` Dave Hansen
2018-08-24 18:11 ` Wei Yang
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