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Date: Wed, 28 Dec 2022 15:22:06 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Huang Ying <ying.huang@...el.com> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>, Yang Shi <shy828301@...il.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, Oscar Salvador <osalvador@...e.de>, Matthew Wilcox <willy@...radead.org>, Bharata B Rao <bharata@....com>, Alistair Popple <apopple@...dia.com>, haoxin <xhao@...ux.alibaba.com> Subject: Re: [PATCH 5/8] migrate_pages: batch _unmap and _move On Tue, 27 Dec 2022 08:28:56 +0800 Huang Ying <ying.huang@...el.com> wrote: > In this patch the _unmap and _move stage of the folio migration is > batched. That for, previously, it is, > > for each folio > _unmap() > _move() > > Now, it is, > > for each folio > _unmap() > for each folio > _move() > > Based on this, we can batch the TLB flushing and use some hardware > accelerator to copy folios between batched _unmap and batched _move > stages. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1027,8 +1027,32 @@ static void __migrate_folio_extract(struct folio *dst, > dst->private = NULL; > } > > +static void migrate_folio_undo_src(struct folio *src, > + int page_was_mapped, > + struct anon_vma *anon_vma, > + struct list_head *ret) > +{ > + if (page_was_mapped) > + remove_migration_ptes(src, src, false); > + if (anon_vma) > + put_anon_vma(anon_vma); > + folio_unlock(src); > + list_move_tail(&src->lru, ret); > +} > + > +static void migrate_folio_undo_dst(struct folio *dst, > + free_page_t put_new_page, > + unsigned long private) > +{ > + folio_unlock(dst); > + if (put_new_page) > + put_new_page(&dst->page, private); > + else > + folio_put(dst); > +} What do the above do? Are they so obvious that no comments are needed? > static int __migrate_folio_unmap(struct folio *src, struct folio *dst, > - int force, enum migrate_mode mode) > + int force, bool force_lock, enum migrate_mode mode) > { > int rc = -EAGAIN; > int page_was_mapped = 0; > @@ -1055,6 +1079,11 @@ static int __migrate_folio_unmap(struct folio *src, struct folio *dst, > if (current->flags & PF_MEMALLOC) > goto out; > > + if (!force_lock) { > + rc = -EDEADLOCK; > + goto out; > + } Please document the use of EDEADLOCK in this code. What does it signify? > folio_lock(src); > } >
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