李真能 <lizhenneng@xxxxxxxxxx> writes: > ---- > > > > > > 主 题：Re: [PATCH] migrate_pages: modify max number of pages to migrate in batch > 日 期：2024-06-25 09:17 > 发件人：ying.huang > 收件人：李真能; > > Hi, Zhenneng, > > Zhenneng Li writes: > >> 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. > > Yes. It's not HPAGE_PMD_NR exactly. > >> Please refer to the patch: 42012e0436d4(migrate_pages: restrict number >> of pages to migrate in batch) >> >> Signed-off-by: Zhenneng Li >> --- >> mm/migrate.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 781979567f64..7a4b37aac9e8 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1961,7 +1961,7 @@ int migrate_pages(struct list_head *from, new_folio_t get_new_folio, >> break; >> } >> if (nr_pages >= NR_MAX_BATCHED_MIGRATION) >> - list_cut_before(&folios, from, &folio2->lru); >> + list_cut_before(&folios, from, &folio->lru); > > If the first entry of the list "from" is a THP with size HPAGE_PMD_NR, > "folio" will be the first entry of from, so that "folios" will be empty. > Right? > > Yes, It's right, so we can check whether it is the first entry of the list "from", new patch are as follows(attachment is > patch file): > 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) > I don't think that it's necessary to change this. Yes, the max batch number of the page migration may be 2*HPAGE_PMD_NR-1. Does it cause any latency issue for you? > >> else >> list_splice_init(from, &folios); >> if (mode == MIGRATE_ASYNC) -- Best Regards, Huang, Ying
