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Message-ID: <754fa87f-48a1-b086-c258-6f74375dec29@redhat.com>
Date:   Mon, 24 Jul 2023 14:17:29 +0200
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Subject: Re: [PATCH v2 2/2] mm/compaction: avoid unneeded pageblock_end_pfn
 when no_set_skip_hint is set
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To:     Kemeng Shi <shikemeng@huawei.com>, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        baolin.wang@linux.alibaba.com
References: <20230721150957.2058634-1-shikemeng@huawei.com>
 <20230721150957.2058634-3-shikemeng@huawei.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230721150957.2058634-3-shikemeng@huawei.com>
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On 21.07.23 17:09, Kemeng Shi wrote:
> Move pageblock_end_pfn after no_set_skip_hint check to avoid unneeded
> pageblock_end_pfn if no_set_skip_hint is set.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>   mm/compaction.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index c0d8d08fc163..9b7a0a69e19f 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -458,12 +458,12 @@ static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
>   {
>   	struct zone *zone = cc->zone;
>   
> -	pfn = pageblock_end_pfn(pfn);
> -
>   	/* Set for isolation rather than compaction */
>   	if (cc->no_set_skip_hint)
>   		return;
>   
> +	pfn = pageblock_end_pfn(pfn);
> +
>   	if (pfn > zone->compact_cached_migrate_pfn[0])
>   		zone->compact_cached_migrate_pfn[0] = pfn;
>   	if (cc->mode != MIGRATE_ASYNC &&

I'm pretty sure the compiler can to optimize this -- there should not be 
any function call involved, so the compiler can reorder as it pleases.

Anyhow, change itself looks good.

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb