| Message ID | 20240629234155.53524-1-21cnbao@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/vmscan: drop checking if _deferred_list is empty before using TTU_SYNC | expand |
On 30/06/2024 00:41, Barry Song wrote: > From: Barry Song <v-songbaohua@oppo.com> > > The optimization of list_empty(&folio->_deferred_list) aimed to prevent > increasing the PTL duration when a large folio is partially unmapped, > for example, from subpage 0 to subpage (nr - 2). > > But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during > shrink_folio_list()") actually splits this kind of large folios. This > makes the "optimization" useless. > > Signed-off-by: Barry Song <v-songbaohua@oppo.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Ryan Roberts <ryan.roberts@arm.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > --- > -v1 > * I remember David and Ryan once suggested that this check could be dropped > while the patch was being pulled into mm-unstable. However, for some reason, > I forgot to request squashing this change. > > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 3d4c681c6d40..0761f91b407f 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > * try_to_unmap acquire PTL from the first PTE, > * eliminating the influence of temporary PTE values. > */ > - if (folio_test_large(folio) && list_empty(&folio->_deferred_list)) > + if (folio_test_large(folio)) As it stands, the list_empty() technically needs a data_race() annotation. I think your original patch went into v6.10-rc1? If so, perhaps it makes sense to try to get this into the next rc? > flags |= TTU_SYNC; > > try_to_unmap(folio, flags);
On 30.06.24 01:41, Barry Song wrote: > From: Barry Song <v-songbaohua@oppo.com> > > The optimization of list_empty(&folio->_deferred_list) aimed to prevent > increasing the PTL duration when a large folio is partially unmapped, > for example, from subpage 0 to subpage (nr - 2). > > But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during > shrink_folio_list()") actually splits this kind of large folios. This > makes the "optimization" useless. > > Signed-off-by: Barry Song <v-songbaohua@oppo.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Ryan Roberts <ryan.roberts@arm.com> > --- > -v1 > * I remember David and Ryan once suggested that this check could be dropped > while the patch was being pulled into mm-unstable. However, for some reason, > I forgot to request squashing this change. > > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 3d4c681c6d40..0761f91b407f 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > * try_to_unmap acquire PTL from the first PTE, > * eliminating the influence of temporary PTE values. > */ > - if (folio_test_large(folio) && list_empty(&folio->_deferred_list)) > + if (folio_test_large(folio)) > flags |= TTU_SYNC; > > try_to_unmap(folio, flags); Reviewed-by: David Hildenbrand <david@redhat.com>
On Mon, Jul 1, 2024 at 8:48 PM Ryan Roberts <ryan.roberts@arm.com> wrote: > > On 30/06/2024 00:41, Barry Song wrote: > > From: Barry Song <v-songbaohua@oppo.com> > > > > The optimization of list_empty(&folio->_deferred_list) aimed to prevent > > increasing the PTL duration when a large folio is partially unmapped, > > for example, from subpage 0 to subpage (nr - 2). > > > > But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during > > shrink_folio_list()") actually splits this kind of large folios. This > > makes the "optimization" useless. > > > > Signed-off-by: Barry Song <v-songbaohua@oppo.com> > > Cc: David Hildenbrand <david@redhat.com> > > Cc: Ryan Roberts <ryan.roberts@arm.com> > > Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > > > --- > > -v1 > > * I remember David and Ryan once suggested that this check could be dropped > > while the patch was being pulled into mm-unstable. However, for some reason, > > I forgot to request squashing this change. > > > > mm/vmscan.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 3d4c681c6d40..0761f91b407f 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > > * try_to_unmap acquire PTL from the first PTE, > > * eliminating the influence of temporary PTE values. > > */ > > - if (folio_test_large(folio) && list_empty(&folio->_deferred_list)) > > + if (folio_test_large(folio)) > > As it stands, the list_empty() technically needs a data_race() annotation. I > think your original patch went into v6.10-rc1? If so, perhaps it makes sense to > try to get this into the next rc? Either way is fine. Hi Andrew, if you include it for the next RC, could you please add this tag? Fixes: 73bc32875ee9 ("mm: hold PTL from the first PTE while reclaiming a large folio") And an additional changelog: Additionally, the list_empty() technically requires a data_race() annotation. > > > flags |= TTU_SYNC; > > > > try_to_unmap(folio, flags); > Thanks Barry
On Mon, 1 Jul 2024 21:35:41 +1200 Barry Song <21cnbao@gmail.com> wrote: > > > +++ b/mm/vmscan.c > > > @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > > > * try_to_unmap acquire PTL from the first PTE, > > > * eliminating the influence of temporary PTE values. > > > */ > > > - if (folio_test_large(folio) && list_empty(&folio->_deferred_list)) > > > + if (folio_test_large(folio)) > > > > As it stands, the list_empty() technically needs a data_race() annotation. I > > think your original patch went into v6.10-rc1? If so, perhaps it makes sense to > > try to get this into the next rc? > > Either way is fine. Hi Andrew, if you include it for the next RC, could you > please add this tag? > > Fixes: 73bc32875ee9 ("mm: hold PTL from the first PTE while reclaiming > a large folio") Nope! That invites people to backport this change into kernels which don't contain Ryan's 5ed890ce5147 ("mm: vmscan: avoid split during shrink_folio_list()"). I'll simply queue this in the normal fashion. > And an additional changelog: > > Additionally, the list_empty() technically requires a data_race() annotation. Done, thanks.
diff --git a/mm/vmscan.c b/mm/vmscan.c index 3d4c681c6d40..0761f91b407f 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, * try_to_unmap acquire PTL from the first PTE, * eliminating the influence of temporary PTE values. */ - if (folio_test_large(folio) && list_empty(&folio->_deferred_list)) + if (folio_test_large(folio)) flags |= TTU_SYNC; try_to_unmap(folio, flags);