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[79.242.58.251]) by smtp.gmail.com with ESMTPSA id l9sm3949679wrp.14.2021.07.02.10.54.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Jul 2021 10:54:53 -0700 (PDT) Subject: Re: [PATCH 1/3] mm: sparse: pass section_nr to section_mark_present To: Ohhoon Kwon , akpm@linux-foundation.org, mhocko@suse.com Cc: bhe@redhat.com, rppt@linux.ibm.com, ohkwon1043@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210702094132.6276-1-ohoono.kwon@samsung.com> <20210702094132.6276-2-ohoono.kwon@samsung.com> From: David Hildenbrand Organization: Red Hat Message-ID: Date: Fri, 2 Jul 2021 19:54:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210702094132.6276-2-ohoono.kwon@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02.07.21 11:41, Ohhoon Kwon wrote: > With CONFIG_SPARSEMEM_EXTREME enabled, __section_nr() which converts > mem_section to section_nr could be costly since it iterates all > section roots to check if the given mem_section is in its range. > > On the other hand, __nr_to_section() which converts section_nr to > mem_section can be done in O(1). > > Let's pass section_nr instead of mem_section ptr to > section_mark_present() in order to reduce needless iterations. > > Signed-off-by: Ohhoon Kwon > --- > mm/sparse.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 55c18aff3e42..4a2700e9a65f 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -186,13 +186,14 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn, > * those loops early. > */ > unsigned long __highest_present_section_nr; > -static void section_mark_present(struct mem_section *ms) > +static void section_mark_present(unsigned long section_nr) > { > - unsigned long section_nr = __section_nr(ms); > + struct mem_section *ms; > > if (section_nr > __highest_present_section_nr) > __highest_present_section_nr = section_nr; > > + ms = __nr_to_section(section_nr); > ms->section_mem_map |= SECTION_MARKED_PRESENT; > } > > @@ -279,7 +280,7 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en > if (!ms->section_mem_map) { > ms->section_mem_map = sparse_encode_early_nid(nid) | > SECTION_IS_ONLINE; > - section_mark_present(ms); > + section_mark_present(section); > } > } > } > @@ -933,7 +934,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, > > ms = __nr_to_section(section_nr); > set_section_nid(section_nr, nid); > - section_mark_present(ms); > + section_mark_present(section_nr); > > /* Align memmap to section boundary in the subsection case */ > if (section_nr_to_pfn(section_nr) != start_pfn) > Fine for me either like this, or as Michal suggested. It's an internal helper either way. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb