Messages in this thread | | | Subject | Re: [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru | From | Konstantin Khlebnikov <> | Date | Fri, 10 Jan 2020 11:49:08 +0300 |
| |
On 25/12/2019 12.04, Alex Shi wrote: > From the commit_charge's explanations and mem_cgroup_commit_charge > comments, as well as call path when lrucare is ture, The lru_lock is > just to guard the task migration(which would be lead to move_account) > So it isn't needed when !PageLRU, and better be fold into PageLRU to > reduce lock contentions. > > Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: cgroups@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/memcontrol.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index c5b5f74cfd4d..0ad10caabc3d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2572,12 +2572,11 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) > > static void lock_page_lru(struct page *page, int *isolated) > { > - pg_data_t *pgdat = page_pgdat(page); > - > - spin_lock_irq(&pgdat->lru_lock); > if (PageLRU(page)) { > + pg_data_t *pgdat = page_pgdat(page); > struct lruvec *lruvec; > > + spin_lock_irq(&pgdat->lru_lock);
That's wrong. Here PageLRU must be checked again under lru_lock.
Also I don't like these functions: - called lock/unlock but actually also isolates - used just once - pgdat evaluated twice
> lruvec = mem_cgroup_page_lruvec(page, pgdat); > ClearPageLRU(page); > del_page_from_lru_list(page, lruvec, page_lru(page)); > @@ -2588,17 +2587,17 @@ static void lock_page_lru(struct page *page, int *isolated) > > static void unlock_page_lru(struct page *page, int isolated) > { > - pg_data_t *pgdat = page_pgdat(page); > > if (isolated) { > + pg_data_t *pgdat = page_pgdat(page); > struct lruvec *lruvec; > > lruvec = mem_cgroup_page_lruvec(page, pgdat); > VM_BUG_ON_PAGE(PageLRU(page), page); > SetPageLRU(page); > add_page_to_lru_list(page, lruvec, page_lru(page)); > + spin_unlock_irq(&pgdat->lru_lock); > } > - spin_unlock_irq(&pgdat->lru_lock); > } > > static void commit_charge(struct page *page, struct mem_cgroup *memcg, >
| |