On 24 Jan 2022, at 9:02, Mel Gorman wrote:

On Wed, Jan 19, 2022 at 02:06:17PM -0500, Zi Yan wrote:

quoted

From: Zi Yan <ziy@nvidia.com>

This is done in addition to MIGRATE_ISOLATE pageblock merge avoidance.
It prepares for the upcoming removal of the MAX_ORDER-1 alignment
requirement for CMA and alloc_contig_range().

MIGRARTE_HIGHATOMIC should not merge with other migratetypes like
MIGRATE_ISOLATE and MIGRARTE_CMA[1], so this commit prevents that too.
Also add MIGRARTE_HIGHATOMIC to fallbacks array for completeness.

[1] https://lore.kernel.org/linux-mm/20211130100853.GP3366@techsingularity.net/ (local)

Signed-off-by: Zi Yan <ziy@nvidia.com>

<SNIP>

@@ -2484,6 +2483,7 @@ static int fallbacks[MIGRATE_TYPES][3] = {
 	[MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
 	[MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
 	[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
+	[MIGRATE_HIGHATOMIC] = { MIGRATE_TYPES }, /* Never used */
 #ifdef CONFIG_CMA
 	[MIGRATE_CMA]         = { MIGRATE_TYPES }, /* Never used */
 #endif

If it's never used, why is it added?

Just to make the fallbacks list complete, since MIGRATE_CMA and
MIGRATE_ISOLATE are in the list. Instead, I can remove MIGRATE_CMA and
MIGRATE_ISOLATE. WDYT?

Otherwise looks fine so

Acked-by: Mel Gorman <redacted>

Thanks.

--
Best Regards,
Yan, Zi