回复: Re: [PATCH] migrate_pages: modify max number of pages to migrate in batch

[李真能 <lizhenneng@kylinos.cn>]

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From 25c3d2df1d38b49f389234e074978d05946a0a63 Mon Sep 17 00:00:00 2001
From: Zhenneng Li <lizhenneng@kylinos.cn>
Date: Mon, 24 Jun 2024 12:19:08 +0800
Subject: [PATCH] migrate_pages: modify max number of pages to migrate in batch

We restrict the number of pages to be migrated to no more than
HPAGE_PMD_NR or NR_MAX_BATCHED_MIGRATION, but in fact, the
number of pages to be migrated may reach 2*HPAGE_PMD_NR-1 or 2
*NR_MAX_BATCHED_MIGRATION-1, it's not in inconsistent with the context.

Please refer to the patch: 42012e0436d4(migrate_pages: restrict number
of pages to migrate in batch)

Signed-off-by: Zhenneng Li <lizhenneng@kylinos.cn>
---
 mm/migrate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 781979567f64..cce8e2b85e89 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1957,11 +1957,12 @@ int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
 		}
 
 		nr_pages += folio_nr_pages(folio);
-		if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
+		if ((nr_pages >= NR_MAX_BATCHED_MIGRATION) &&
+		    (!list_first_entry(from, struct folio, lru)))
 			break;
 	}
 	if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
-		list_cut_before(&folios, from, &folio2->lru);
+		list_cut_before(&folios, from, &folio->lru);
 	else
 		list_splice_init(from, &folios);
 	if (mode == MIGRATE_ASYNC)
-- 
2.25.1