From: Dave Hansen <dave.hansen@intel.com>
To: Wei Yang <richard.weiyang@gmail.com>,
akpm@linux-foundation.org, mhocko@suse.com, rientjes@google.com
Cc: 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: Thu, 23 Aug 2018 17:11:48 -0700 [thread overview]
Message-ID: <cc817bc8-bced-fb07-cb2d-c122463380a7@intel.com> (raw)
In-Reply-To: <20180823130732.9489-2-richard.weiyang@gmail.com>
On 08/23/2018 06:07 AM, Wei Yang wrote:
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -78,7 +78,7 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
> unsigned long root = SECTION_NR_TO_ROOT(section_nr);
> struct mem_section *section;
>
> - if (mem_section[root])
> + if (likely(mem_section[root]))
> return -EEXIST;
We could add likely()/unlikely() to approximately a billion if()s around
the kernel if we felt like it. We don't because it's messy and it
actually takes away choices from the compiler.
Please don't send patches like this unless you have some *actual*
analysis that shows the benefit of the patch. Performance numbers are best.
next prev parent reply other threads:[~2018-08-24 0:11 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 [this message]
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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