Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify lruvec_holds_page_lru_lock
On Thu, Apr 15, 2021 at 1:49 AM Johannes Weiner wrote: > > On Wed, Apr 14, 2021 at 06:00:42PM +0800, Muchun Song wrote: > > On Wed, Apr 14, 2021 at 5:44 PM Michal Hocko wrote: > > > > > > On Tue 13-04-21 14:51:50, Muchun Song wrote: > > > > We already have a helper lruvec_memcg() to get the memcg from lruvec, we > > > > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So > > > > use > > > > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the > > > > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic > > > > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat > > > > to simplify the code. We can have a single definition for this function > > > > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and > > > > CONFIG_MEMCG. > > > > > > Neat. While you are at it wouldn't it make sesne to rename the function > > > as well. I do not want to bikeshed but this is really a misnomer. it > > > doesn't check anything about locking. page_belongs_lruvec? > > > > Right. lruvec_holds_page_lru_lock is used to check whether > > the page belongs to the lruvec. page_belongs_lruvec > > obviously more clearer. I can rename it to > > page_belongs_lruvec the next version. > > This sounds strange to me, I think 'belongs' needs a 'to' to be > correct, so page_belongs_to_lruvec(). Still kind of a mouthful. > > page_matches_lruvec()? > I prefer this name. If you also agree, I will use this name. Thanks. > page_from_lruvec()?
Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify lruvec_holds_page_lru_lock
On Wed 14-04-21 13:49:56, Johannes Weiner wrote: > On Wed, Apr 14, 2021 at 06:00:42PM +0800, Muchun Song wrote: > > On Wed, Apr 14, 2021 at 5:44 PM Michal Hocko wrote: > > > > > > On Tue 13-04-21 14:51:50, Muchun Song wrote: > > > > We already have a helper lruvec_memcg() to get the memcg from lruvec, we > > > > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So > > > > use > > > > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the > > > > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic > > > > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat > > > > to simplify the code. We can have a single definition for this function > > > > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and > > > > CONFIG_MEMCG. > > > > > > Neat. While you are at it wouldn't it make sesne to rename the function > > > as well. I do not want to bikeshed but this is really a misnomer. it > > > doesn't check anything about locking. page_belongs_lruvec? > > > > Right. lruvec_holds_page_lru_lock is used to check whether > > the page belongs to the lruvec. page_belongs_lruvec > > obviously more clearer. I can rename it to > > page_belongs_lruvec the next version. > > This sounds strange to me, I think 'belongs' needs a 'to' to be > correct, so page_belongs_to_lruvec(). Still kind of a mouthful. > > page_matches_lruvec()? > > page_from_lruvec()? Any of those is much better than what we have here. -- Michal Hocko SUSE Labs
Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify lruvec_holds_page_lru_lock
On Wed, Apr 14, 2021 at 06:00:42PM +0800, Muchun Song wrote: > On Wed, Apr 14, 2021 at 5:44 PM Michal Hocko wrote: > > > > On Tue 13-04-21 14:51:50, Muchun Song wrote: > > > We already have a helper lruvec_memcg() to get the memcg from lruvec, we > > > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use > > > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the > > > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic > > > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat > > > to simplify the code. We can have a single definition for this function > > > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and > > > CONFIG_MEMCG. > > > > Neat. While you are at it wouldn't it make sesne to rename the function > > as well. I do not want to bikeshed but this is really a misnomer. it > > doesn't check anything about locking. page_belongs_lruvec? > > Right. lruvec_holds_page_lru_lock is used to check whether > the page belongs to the lruvec. page_belongs_lruvec > obviously more clearer. I can rename it to > page_belongs_lruvec the next version. This sounds strange to me, I think 'belongs' needs a 'to' to be correct, so page_belongs_to_lruvec(). Still kind of a mouthful. page_matches_lruvec()? page_from_lruvec()?
Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify lruvec_holds_page_lru_lock
On Wed, Apr 14, 2021 at 5:44 PM Michal Hocko wrote:
>
> On Tue 13-04-21 14:51:50, Muchun Song wrote:
> > We already have a helper lruvec_memcg() to get the memcg from lruvec, we
> > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use
> > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the
> > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic
> > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat
> > to simplify the code. We can have a single definition for this function
> > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and
> > CONFIG_MEMCG.
>
> Neat. While you are at it wouldn't it make sesne to rename the function
> as well. I do not want to bikeshed but this is really a misnomer. it
> doesn't check anything about locking. page_belongs_lruvec?
Right. lruvec_holds_page_lru_lock is used to check whether
the page belongs to the lruvec. page_belongs_lruvec
obviously more clearer. I can rename it to
page_belongs_lruvec the next version.
>
> > Signed-off-by: Muchun Song
> > Acked-by: Johannes Weiner
>
> Acked-by: Michal Hocko
Thanks.
>
> > ---
> > include/linux/memcontrol.h | 31 +++
> > 1 file changed, 7 insertions(+), 24 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 4f49865c9958..38b8d3fb24ff 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -755,22 +755,6 @@ static inline struct lruvec
> > *mem_cgroup_page_lruvec(struct page *page)
> > return mem_cgroup_lruvec(memcg, pgdat);
> > }
> >
> > -static inline bool lruvec_holds_page_lru_lock(struct page *page,
> > - struct lruvec *lruvec)
> > -{
> > - pg_data_t *pgdat = page_pgdat(page);
> > - const struct mem_cgroup *memcg;
> > - struct mem_cgroup_per_node *mz;
> > -
> > - if (mem_cgroup_disabled())
> > - return lruvec == &pgdat->__lruvec;
> > -
> > - mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
> > - memcg = page_memcg(page) ? : root_mem_cgroup;
> > -
> > - return lruvec->pgdat == pgdat && mz->memcg == memcg;
> > -}
> > -
> > struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
> >
> > struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
> > @@ -1229,14 +1213,6 @@ static inline struct lruvec
> > *mem_cgroup_page_lruvec(struct page *page)
> > return &pgdat->__lruvec;
> > }
> >
> > -static inline bool lruvec_holds_page_lru_lock(struct page *page,
> > - struct lruvec *lruvec)
> > -{
> > - pg_data_t *pgdat = page_pgdat(page);
> > -
> > - return lruvec == &pgdat->__lruvec;
> > -}
> > -
> > static inline void lruvec_memcg_debug(struct lruvec *lruvec, struct page
> > *page)
> > {
> > }
> > @@ -1518,6 +1494,13 @@ static inline void
> > unlock_page_lruvec_irqrestore(struct lruvec *lruvec,
> > spin_unlock_irqrestore(&lruvec->lru_lock, flags);
> > }
> >
> > +static inline bool lruvec_holds_page_lru_lock(struct page *page,
> > + struct lruvec *lruvec)
> > +{
> > + return lruvec_pgdat(lruvec) == page_pgdat(page) &&
> > +lruvec_memcg(lruvec) == page_memcg(page);
> > +}
> > +
> > /* Don't lock again iff page's lruvec locked */
> > static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
> > struct lruvec *locked_lruvec)
> > --
> > 2.11.0
>
> --
> Michal Hocko
> SUSE Labs
