linux-kernel - Re: [PATCH v2 2/2] mm/compaction: avoid unneeded pageblock_end_pfn when no_set_skip

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Date:   Mon, 24 Jul 2023 14:17:29 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kemeng Shi <shikemeng@...wei.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        baolin.wang@...ux.alibaba.com
Subject: Re: [PATCH v2 2/2] mm/compaction: avoid unneeded pageblock_end_pfn
 when no_set_skip_hint is set

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@...wei.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.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@...hat.com>

-- 
Cheers,

David / dhildenb