From: Alexander Duyck <alexander.duyck@gmail.com>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Tejun Heo <tj@kernel.org>, Hugh Dickins <hughd@google.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
Matthew Wilcox <willy@infradead.org>,
Johannes Weiner <hannes@cmpxchg.org>,
kbuild test robot <lkp@intel.com>, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
cgroups@vger.kernel.org, Shakeel Butt <shakeelb@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Wei Yang <richard.weiyang@gmail.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Rong Chen <rong.a.chen@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: Re: [PATCH v17 18/21] mm/lru: introduce the relock_page_lruvec function
Date: Wed, 29 Jul 2020 10:52:01 -0700 [thread overview]
Message-ID: <CAKgT0UdFDcz=CQ+6mzcjh-apwy3UyPqAuOozvYr+2PSCNQrENA@mail.gmail.com> (raw)
In-Reply-To: <1595681998-19193-19-git-send-email-alex.shi@linux.alibaba.com>
On Sat, Jul 25, 2020 at 6:00 AM Alex Shi <alex.shi@linux.alibaba.com> wrote:
>
> Use this new function to replace repeated same code, no func change.
>
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: linux-kernel@vger.kernel.org
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> ---
> include/linux/memcontrol.h | 40 ++++++++++++++++++++++++++++++++++++++++
> mm/mlock.c | 9 +--------
> mm/swap.c | 33 +++++++--------------------------
> mm/vmscan.c | 8 +-------
> 4 files changed, 49 insertions(+), 41 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 258901021c6c..6e670f991b42 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1313,6 +1313,46 @@ static inline void unlock_page_lruvec_irqrestore(struct lruvec *lruvec,
> spin_unlock_irqrestore(&lruvec->lru_lock, flags);
> }
>
> +/* Don't lock again iff page's lruvec locked */
> +static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
> + struct lruvec *locked_lruvec)
> +{
> + struct pglist_data *pgdat = page_pgdat(page);
> + bool locked;
> +
> + rcu_read_lock();
> + locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec;
> + rcu_read_unlock();
> +
> + if (locked)
> + return locked_lruvec;
> +
> + if (locked_lruvec)
> + unlock_page_lruvec_irq(locked_lruvec);
> +
> + return lock_page_lruvec_irq(page);
> +}
> +
> +/* Don't lock again iff page's lruvec locked */
> +static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page,
> + struct lruvec *locked_lruvec, unsigned long *flags)
> +{
> + struct pglist_data *pgdat = page_pgdat(page);
> + bool locked;
> +
> + rcu_read_lock();
> + locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec;
> + rcu_read_unlock();
> +
> + if (locked)
> + return locked_lruvec;
> +
> + if (locked_lruvec)
> + unlock_page_lruvec_irqrestore(locked_lruvec, *flags);
> +
> + return lock_page_lruvec_irqsave(page, flags);
> +}
> +
So looking these over they seem to be pretty inefficient for what they
do. Basically in worst case (locked_lruvec == NULL) you end up calling
mem_cgoup_page_lruvec and all the rcu_read_lock/unlock a couple times
for a single page. It might make more sense to structure this like:
if (locked_lruvec) {
if (lruvec_holds_page_lru_lock(page, locked_lruvec))
return locked_lruvec;
unlock_page_lruvec_irqrestore(locked_lruvec, *flags);
}
return lock_page_lruvec_irqsave(page, flags);
The other piece that has me scratching my head is that I wonder if we
couldn't do this without needing the rcu_read_lock. For example, what
if we were to compare the page mem_cgroup pointer to the memcg back
pointer stored in the mem_cgroup_per_node? It seems like ordering
things this way would significantly reduce the overhead due to the
pointer chasing to see if the page is in the locked lruvec or not.
> #ifdef CONFIG_CGROUP_WRITEBACK
>
> struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb);
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 5d40d259a931..bc2fb3bfbe7a 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -303,17 +303,10 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
> /* Phase 1: page isolation */
> for (i = 0; i < nr; i++) {
> struct page *page = pvec->pages[i];
> - struct lruvec *new_lruvec;
>
> /* block memcg change in mem_cgroup_move_account */
> lock_page_memcg(page);
> - new_lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
> - if (new_lruvec != lruvec) {
> - if (lruvec)
> - unlock_page_lruvec_irq(lruvec);
> - lruvec = lock_page_lruvec_irq(page);
> - }
> -
> + lruvec = relock_page_lruvec_irq(page, lruvec);
> if (TestClearPageMlocked(page)) {
> /*
> * We already have pin from follow_page_mask()
> diff --git a/mm/swap.c b/mm/swap.c
> index 09edac441eb6..6d9c7288f7de 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -209,19 +209,12 @@ static void pagevec_lru_move_fn(struct pagevec *pvec,
>
> for (i = 0; i < pagevec_count(pvec); i++) {
> struct page *page = pvec->pages[i];
> - struct lruvec *new_lruvec;
>
> /* block memcg migration during page moving between lru */
> if (!TestClearPageLRU(page))
> continue;
>
> - new_lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
> - if (lruvec != new_lruvec) {
> - if (lruvec)
> - unlock_page_lruvec_irqrestore(lruvec, flags);
> - lruvec = lock_page_lruvec_irqsave(page, &flags);
> - }
> -
> + lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
> (*move_fn)(page, lruvec);
>
> SetPageLRU(page);
> @@ -864,17 +857,12 @@ void release_pages(struct page **pages, int nr)
> }
>
> if (PageLRU(page)) {
> - struct lruvec *new_lruvec;
> -
> - new_lruvec = mem_cgroup_page_lruvec(page,
> - page_pgdat(page));
> - if (new_lruvec != lruvec) {
> - if (lruvec)
> - unlock_page_lruvec_irqrestore(lruvec,
> - flags);
> + struct lruvec *prev_lruvec = lruvec;
> +
> + lruvec = relock_page_lruvec_irqsave(page, lruvec,
> + &flags);
> + if (prev_lruvec != lruvec)
> lock_batch = 0;
> - lruvec = lock_page_lruvec_irqsave(page, &flags);
> - }
>
> __ClearPageLRU(page);
> del_page_from_lru_list(page, lruvec, page_off_lru(page));
> @@ -980,15 +968,8 @@ void __pagevec_lru_add(struct pagevec *pvec)
>
> for (i = 0; i < pagevec_count(pvec); i++) {
> struct page *page = pvec->pages[i];
> - struct lruvec *new_lruvec;
> -
> - new_lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
> - if (lruvec != new_lruvec) {
> - if (lruvec)
> - unlock_page_lruvec_irqrestore(lruvec, flags);
> - lruvec = lock_page_lruvec_irqsave(page, &flags);
> - }
>
> + lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
> __pagevec_lru_add_fn(page, lruvec);
> }
> if (lruvec)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 168c1659e430..bdb53a678e7e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4292,15 +4292,9 @@ void check_move_unevictable_pages(struct pagevec *pvec)
>
> for (i = 0; i < pvec->nr; i++) {
> struct page *page = pvec->pages[i];
> - struct lruvec *new_lruvec;
>
> pgscanned++;
> - new_lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
> - if (lruvec != new_lruvec) {
> - if (lruvec)
> - unlock_page_lruvec_irq(lruvec);
> - lruvec = lock_page_lruvec_irq(page);
> - }
> + lruvec = relock_page_lruvec_irq(page, lruvec);
>
> if (!PageLRU(page) || !PageUnevictable(page))
> continue;
> --
> 1.8.3.1
>
next prev parent reply other threads:[~2020-07-29 17:52 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-25 12:59 [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-25 12:59 ` [PATCH v17 01/21] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-08-06 3:47 ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 02/21] mm/page_idle: no unlikely double check for idle page counting Alex Shi
2020-07-25 12:59 ` [PATCH v17 03/21] mm/compaction: correct the comments of compact_defer_shift Alex Shi
2020-07-27 17:29 ` Alexander Duyck
2020-07-28 11:59 ` Alex Shi
2020-07-28 14:17 ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 04/21] mm/compaction: rename compact_deferred as compact_should_defer Alex Shi
2020-07-25 12:59 ` [PATCH v17 05/21] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi
2020-07-25 12:59 ` [PATCH v17 06/21] mm/thp: clean up lru_add_page_tail Alex Shi
2020-07-25 12:59 ` [PATCH v17 07/21] mm/thp: remove code path which never got into Alex Shi
2020-07-25 12:59 ` [PATCH v17 08/21] mm/thp: narrow lru locking Alex Shi
2020-07-25 12:59 ` [PATCH v17 09/21] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2020-07-25 12:59 ` [PATCH v17 10/21] mm/swap: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 11/21] mm/lru: move lru_lock holding in func lru_note_cost_page Alex Shi
2020-08-05 21:18 ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 12/21] mm/lru: move lock into lru_note_cost Alex Shi
2020-07-25 12:59 ` [PATCH v17 13/21] mm/lru: introduce TestClearPageLRU Alex Shi
2020-07-29 3:53 ` Alex Shi
2020-08-05 22:43 ` Alexander Duyck
2020-08-06 1:54 ` Alex Shi
2020-08-06 14:41 ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alex Shi
2020-08-04 21:35 ` Alexander Duyck
2020-08-06 18:38 ` Alexander Duyck
2020-08-07 3:24 ` Alex Shi
2020-08-07 14:51 ` Alexander Duyck
2020-08-10 13:10 ` Alex Shi
2020-08-10 14:41 ` Alexander Duyck
2020-08-11 8:22 ` Alex Shi
2020-08-11 14:47 ` Alexander Duyck
2020-08-12 11:43 ` Alex Shi
2020-08-12 12:16 ` Alex Shi
2020-08-12 16:51 ` Alexander Duyck
2020-08-13 1:46 ` Alex Shi
2020-08-13 2:17 ` Alexander Duyck
2020-08-13 3:52 ` Alex Shi
2020-08-13 4:02 ` [RFC PATCH 0/3] " Alexander Duyck
2020-08-13 4:02 ` [RFC PATCH 1/3] mm: Drop locked from isolate_migratepages_block Alexander Duyck
2020-08-13 6:56 ` Alex Shi
2020-08-13 14:32 ` Alexander Duyck
2020-08-14 7:25 ` Alex Shi
2020-08-13 7:44 ` Alex Shi
2020-08-13 14:26 ` Alexander Duyck
2020-08-13 4:02 ` [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip Alexander Duyck
2020-08-14 7:19 ` Alex Shi
2020-08-14 14:24 ` Alexander Duyck
2020-08-14 21:15 ` Alexander Duyck
[not found] ` <650ab639-e66f-5ca6-a9a5-31e61c134ae7@linux.alibaba.com>
2020-08-17 15:38 ` Alexander Duyck
2020-08-18 6:50 ` Alex Shi
2020-08-13 4:02 ` [RFC PATCH 3/3] mm: Identify compound pages sooner in isolate_migratepages_block Alexander Duyck
2020-08-14 7:20 ` Alex Shi
2020-08-17 22:58 ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page() Alex Shi
2020-07-25 12:59 ` [PATCH v17 16/21] mm/swap: serialize memcg changes in pagevec_lru_move_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 17/21] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-07-27 23:34 ` Alexander Duyck
2020-07-28 7:15 ` Alex Shi
2020-07-28 11:19 ` Alex Shi
2020-07-28 14:54 ` Alexander Duyck
2020-07-29 1:00 ` Alex Shi
2020-07-29 1:27 ` Alexander Duyck
2020-07-29 2:27 ` Alex Shi
2020-07-28 15:39 ` Alex Shi
2020-07-28 15:55 ` Alexander Duyck
2020-07-29 0:48 ` Alex Shi
2020-07-29 3:54 ` Alex Shi
2020-08-06 7:41 ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 18/21] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-07-29 17:52 ` Alexander Duyck [this message]
2020-07-30 6:08 ` Alex Shi
2020-07-31 14:20 ` Alexander Duyck
2020-07-31 21:14 ` [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid alexander.h.duyck
2020-07-31 23:54 ` Alex Shi
2020-08-02 18:20 ` Alexander Duyck
2020-08-04 6:13 ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 19/21] mm/vmscan: use relock for move_pages_to_lru Alex Shi
2020-08-03 22:49 ` Alexander Duyck
2020-08-04 6:23 ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 20/21] mm/pgdat: remove pgdat lru_lock Alex Shi
2020-08-03 22:42 ` Alexander Duyck
2020-08-03 22:45 ` Alexander Duyck
2020-08-04 6:22 ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 21/21] mm/lru: revise the comments of lru_lock Alex Shi
2020-08-03 22:37 ` Alexander Duyck
2020-08-04 10:04 ` Alex Shi
2020-08-04 14:29 ` Alexander Duyck
2020-08-06 1:39 ` Alex Shi
2020-08-06 16:27 ` Alexander Duyck
2020-07-27 5:40 ` [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-29 14:49 ` Alex Shi
2020-07-29 18:06 ` Hugh Dickins
2020-07-30 2:16 ` Alex Shi
2020-08-03 15:07 ` Michal Hocko
2020-08-04 6:14 ` Alex Shi
2020-07-31 21:31 ` Alexander Duyck
2020-08-04 8:36 ` Alex Shi
2020-08-04 8:36 ` Alex Shi
2020-08-04 8:37 ` Alex Shi
2020-08-04 8:37 ` Alex Shi
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