[PATCH v2 0/2] Two minor cleanups for compaction

[PATCH v2 0/2] Two minor cleanups for compaction

[Kemeng Shi]

v1->v2:
 collect reviewed-by from Baolin to patch 2.

This series contains two random cleanups for compaction.
Patch 1 correct wrong comment in fast_isolate_freepages.
Patch 2 avoid to call unneeded pageblock_end_pfn when no_set_skip_hint
is set.
Thanks!

Kemeng Shi (2):
  mm/compaction: correct comment of candidate pfn in
    fast_isolate_freepages
  mm/compaction: avoid unneeded pageblock_end_pfn when no_set_skip_hint
    is set

 mm/compaction.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

-- 
2.30.0

[PATCH v2 2/2] mm/compaction: avoid unneeded pageblock_end_pfn when no_set_skip_hint is set

[Kemeng Shi]

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 &&
-- 
2.30.0

Re: [PATCH v2 2/2] mm/compaction: avoid unneeded pageblock_end_pfn when no_set_skip_hint is set

[David Hildenbrand]

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

Re: [PATCH v2 1/2] mm/compaction: correct comment of candidate pfn in fast_isolate_freepages

[Baolin Wang]

On 7/21/2023 11:09 PM, Kemeng Shi wrote:
> If no preferred one was not found, we will use candidate page with maximum
> pfn > min_pfn which is saved in high_pfn. Correct "minimum" to "maximum
> candidate" in comment.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huawei.com>

Yes, the 'minimum' can be confused. At least to me, it looks good.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

> ---
>   mm/compaction.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index eb1d3d9a422c..c0d8d08fc163 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1526,7 +1526,7 @@ static void fast_isolate_freepages(struct compact_control *cc)
>   				break;
>   		}
>   
> -		/* Use a minimum pfn if a preferred one was not found */
> +		/* Use a maximum candidate pfn if a preferred one was not found */
>   		if (!page && high_pfn) {
>   			page = pfn_to_page(high_pfn);
>