2021-04-01 21:25:47

by Sergei Trofimovich

Subject: [PATCH] mm: page_owner: fetch backtrace only for tracked pages

Very minor optimization.

CC: Andrew Morton <[email protected]>
CC: [email protected]
Signed-off-by: Sergei Trofimovich <[email protected]>
---
mm/page_owner.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 63e4ecaba97b..7147fd34a948 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -140,14 +140,14 @@ void __reset_page_owner(struct page *page, unsigned int order)
{
int i;
struct page_ext *page_ext;
- depot_stack_handle_t handle = 0;
+ depot_stack_handle_t handle;
struct page_owner *page_owner;

- handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
-
page_ext = lookup_page_ext(page);
if (unlikely(!page_ext))
return;
+
+ handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
for (i = 0; i < (1 << order); i++) {
__clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
page_owner = get_page_owner(page_ext);
--
2.31.1

2021-04-07 21:25:12

by Vlastimil Babka

Subject: Re: [PATCH] mm: page_owner: fetch backtrace only for tracked pages

On 4/1/21 11:24 PM, Sergei Trofimovich wrote:
> Very minor optimization.

I'm not entirely sure about accuracy of "only for tracked pages". Missing
page_ext is something I'm not even sure how possible it is in practice, probably
just an error condition (failed to be allocated?). Or did you observe this in
practice? But anyway, the change is not wrong.

> CC: Andrew Morton <[email protected]>
> CC: [email protected]
> Signed-off-by: Sergei Trofimovich <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

> ---
> mm/page_owner.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 63e4ecaba97b..7147fd34a948 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -140,14 +140,14 @@ void __reset_page_owner(struct page *page, unsigned int order)
> {
> int i;
> struct page_ext *page_ext;
> - depot_stack_handle_t handle = 0;
> + depot_stack_handle_t handle;
> struct page_owner *page_owner;
>
> - handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
> -
> page_ext = lookup_page_ext(page);
> if (unlikely(!page_ext))
> return;
> +
> + handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
> for (i = 0; i < (1 << order); i++) {
> __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
> page_owner = get_page_owner(page_ext);
>

2021-04-07 22:49:45

by Sergei Trofimovich

Subject: Re: [PATCH] mm: page_owner: fetch backtrace only for tracked pages

On Wed, Apr 07, 2021 at 05:49:14PM +0200, Vlastimil Babka wrote:
> On 4/1/21 11:24 PM, Sergei Trofimovich wrote:
> > Very minor optimization.
>
> I'm not entirely sure about accuracy of "only for tracked pages". Missing
> page_ext is something I'm not even sure how possible it is in practice, probably
> just an error condition (failed to be allocated?). Or did you observe this in
> practice? But anyway, the change is not wrong.

Never saw missing 'page_ext' in practice (I also did not check for
it explicitly). I agree "optimization" is misleading. "cleanup"
might be a better wording.

> > CC: Andrew Morton <[email protected]>
> > CC: [email protected]
> > Signed-off-by: Sergei Trofimovich <[email protected]>
>
> Acked-by: Vlastimil Babka <[email protected]>
>
> > ---
> > mm/page_owner.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/page_owner.c b/mm/page_owner.c
> > index 63e4ecaba97b..7147fd34a948 100644
> > --- a/mm/page_owner.c
> > +++ b/mm/page_owner.c
> > @@ -140,14 +140,14 @@ void __reset_page_owner(struct page *page, unsigned int order)
> > {
> > int i;
> > struct page_ext *page_ext;
> > - depot_stack_handle_t handle = 0;
> > + depot_stack_handle_t handle;
> > struct page_owner *page_owner;
> >
> > - handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
> > -
> > page_ext = lookup_page_ext(page);
> > if (unlikely(!page_ext))
> > return;
> > +
> > + handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
> > for (i = 0; i < (1 << order); i++) {
> > __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
> > page_owner = get_page_owner(page_ext);
> >
>

--

Sergei