Messages in this thread | | | Subject | Re: [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru | From | Alex Shi <> | Date | Mon, 13 Jan 2020 17:45:51 +0800 |
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在 2020/1/10 下午4:49, Konstantin Khlebnikov 写道: > 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. Hi, Konstantin,
For logical remain, we can get the lock and then release for !PageLRU. but I still can figure out the problem scenario. Would like to give more hints?
> > > Also I don't like these functions: > - called lock/unlock but actually also isolates > - used just once > - pgdat evaluated twice
That's right. I will fold these functions into commit_charge.
Thanks Alex
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