| Message ID | 20210104065843.5658-1-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one | expand |
On 1/3/21 10:58 PM, Muchun Song wrote: > If the refcount is one when it is migrated, it means that the page > was freed from under us. So we are done and do not need to migrate. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) Thanks! Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
On 04.01.21 07:58, Muchun Song wrote: > If the refcount is one when it is migrated, it means that the page > was freed from under us. So we are done and do not need to migrate. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; > This series seems to fix quite some important cases (thanks). Do we want to cc stable some/all?
On Tue, Jan 5, 2021 at 8:58 AM David Hildenbrand <david@redhat.com> wrote: > > On 04.01.21 07:58, Muchun Song wrote: > > If the refcount is one when it is migrated, it means that the page > > was freed from under us. So we are done and do not need to migrate. > > > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > > --- > > mm/migrate.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/mm/migrate.c b/mm/migrate.c > > index 4385f2fb5d18..a6631c4eb6a6 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > > return -ENOSYS; > > } > > > > + if (page_count(hpage) == 1) { > > + /* page was freed from under us. So we are done. */ > > + putback_active_hugepage(hpage); > > + return MIGRATEPAGE_SUCCESS; > > + } > > + > > new_hpage = get_new_page(hpage, private); > > if (!new_hpage) > > return -ENOMEM; > > > > This series seems to fix quite some important cases (thanks). Do we want > to cc stable some/all? For this particular one, I don't think so IMHO. It is an optimization rather than a bug fix. > > -- > Thanks, > > David / dhildenb > >
On Sun, Jan 3, 2021 at 11:01 PM Muchun Song <songmuchun@bytedance.com> wrote: > > If the refcount is one when it is migrated, it means that the page > was freed from under us. So we are done and do not need to migrate. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + Acked-by: Yang Shi <shy828301@gmail.com> > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; > -- > 2.11.0 > >
On 05.01.21 19:04, Yang Shi wrote: > On Tue, Jan 5, 2021 at 8:58 AM David Hildenbrand <david@redhat.com> wrote: >> >> On 04.01.21 07:58, Muchun Song wrote: >>> If the refcount is one when it is migrated, it means that the page >>> was freed from under us. So we are done and do not need to migrate. >>> >>> Signed-off-by: Muchun Song <songmuchun@bytedance.com> >>> --- >>> mm/migrate.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 4385f2fb5d18..a6631c4eb6a6 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, >>> return -ENOSYS; >>> } >>> >>> + if (page_count(hpage) == 1) { >>> + /* page was freed from under us. So we are done. */ >>> + putback_active_hugepage(hpage); >>> + return MIGRATEPAGE_SUCCESS; >>> + } >>> + >>> new_hpage = get_new_page(hpage, private); >>> if (!new_hpage) >>> return -ENOMEM; >>> >> >> This series seems to fix quite some important cases (thanks). Do we want >> to cc stable some/all? > > For this particular one, I don't think so IMHO. It is an optimization > rather than a bug fix. I'm rather referring to the actual fixes (I received no cover letter so I picked the first patch in the series)
On Mon 04-01-21 14:58:38, Muchun Song wrote: > If the refcount is one when it is migrated, it means that the page > was freed from under us. So we are done and do not need to migrate. Is this common enough that it would warrant the explicit check for each migration? > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; > -- > 2.11.0
On Wed 06-01-21 17:11:39, Michal Hocko wrote: > On Mon 04-01-21 14:58:38, Muchun Song wrote: > > If the refcount is one when it is migrated, it means that the page > > was freed from under us. So we are done and do not need to migrate. > > Is this common enough that it would warrant the explicit check for each > migration? Ups, just noticed that you have posted a newer version. I will follow up there.
diff --git a/mm/migrate.c b/mm/migrate.c index 4385f2fb5d18..a6631c4eb6a6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, return -ENOSYS; } + if (page_count(hpage) == 1) { + /* page was freed from under us. So we are done. */ + putback_active_hugepage(hpage); + return MIGRATEPAGE_SUCCESS; + } + new_hpage = get_new_page(hpage, private); if (!new_hpage) return -ENOMEM;
If the refcount is one when it is migrated, it means that the page was freed from under us. So we are done and do not need to migrate. Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- mm/migrate.c | 6 ++++++ 1 file changed, 6 insertions(+)