Received-SPF: pass (google.com: domain of linux-kernel+bounces-70940-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <63a0f7c4-3c3f-4097-9a24-d1e3fc7b6030@linux.ibm.com>
Date: Mon, 19 Feb 2024 14:04:23 +0530
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 1/3] mm/mempolicy: Use the already fetched local variable
Content-Language: en-US
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Aneesh Kumar <aneesh.kumar@kernel.org>,
        Huang Ying <ying.huang@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>, Ben Widawsky <ben.widawsky@intel.com>,
        Feng Tang <feng.tang@intel.com>, Michal Hocko <mhocko@kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Rik van Riel <riel@surriel.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Matthew Wilcox <willy@infradead.org>,
        Mike Kravetz
 <mike.kravetz@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Hugh Dickins <hughd@google.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Suren Baghdasaryan <surenb@google.com>
References: <9c3f7b743477560d1c5b12b8c111a584a2cc92ee.1708097962.git.donettom@linux.ibm.com>
 <20240218133851.22c22b55460e866a099be5ce@linux-foundation.org>
From: Donet Tom <donettom@linux.ibm.com>
In-Reply-To: <20240218133851.22c22b55460e866a099be5ce@linux-foundation.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit


On 2/19/24 03:08, Andrew Morton wrote:
> On Sat, 17 Feb 2024 01:31:33 -0600 Donet Tom <donettom@linux.ibm.com> wrote:
>
>> Avoid doing a per cpu read and use the local variable thisnid. IMHO
>> this also makes the code more readable.
>>
>> ...
>>
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -2526,7 +2526,7 @@ int mpol_misplaced(struct folio *folio, struct vm_area_struct *vma,
>>   		if (node_isset(curnid, pol->nodes))
>>   			goto out;
>>   		z = first_zones_zonelist(
>> -				node_zonelist(numa_node_id(), GFP_HIGHUSER),
>> +				node_zonelist(thisnid, GFP_HIGHUSER),
>>   				gfp_zone(GFP_HIGHUSER),
>>   				&pol->nodes);
>>   		polnid = zone_to_nid(z->zone);
> 	int thisnid = cpu_to_node(thiscpu);
>
> Is there any dofference between numa_node_id() and
> cpu_to_node(raw_smp_processor_id())?  And it it explicable that we're
> using one here and not the other?

Hi Andrew

Both numa_node_id() and cpu_to_node(raw_smp_processor_id()) return the current execution node id,
Since the current execution node is already fetched at the beginning (thisnid) we can reuse it instead of getting it again.

Thanks
Donet Tom

>