Messages in this thread | | | Subject | Re: [LKP] Re: [mm] be5d0a74c6: will-it-scale.per_thread_ops -9.1% regression | From | Xing Zhengjun <> | Date | Wed, 18 Nov 2020 10:48:47 +0800 |
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On 11/17/2020 12:19 AM, Johannes Weiner wrote: > On Sun, Nov 15, 2020 at 05:55:44PM +0800, kernel test robot wrote: >> >> Greeting, >> >> FYI, we noticed a -9.1% regression of will-it-scale.per_thread_ops due to commit: >> >> >> commit: be5d0a74c62d8da43f9526a5b08cdd18e2bbc37a ("mm: memcontrol: switch to native NR_ANON_MAPPED counter") >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master >> >> >> in testcase: will-it-scale >> on test machine: 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory >> with following parameters: >> >> nr_task: 50% >> mode: thread >> test: page_fault2 >> cpufreq_governor: performance >> ucode: 0x5002f01 > > I suspect it's the lock_page_memcg() in page_remove_rmap(). We already > needed it for shared mappings, and this patch added it to private path > as well, which this test exercises. > > The slowpath for this lock is extremely cold - most of the time it's > just an rcu_read_lock(). But we're still doing the function call. > > Could you try if this patch helps, please?
I apply the patch to Linux mainline v5.10-rc4, Linux-next next-20201117, and "be5d0a74c6", they are all failed. What's your codebase for the patch? I appreciate it if you can rebase the patch to "be5d0a74c6". From "be5d0a74c6" to v5.10-rc4 or next-20201117, there are a lot of commits, they will affect the test result. Thanks.
> > From f6e8e56b369109d1362de2c27ea6601d5c411b2e Mon Sep 17 00:00:00 2001 > From: Johannes Weiner <hannes@cmpxchg.org> > Date: Mon, 16 Nov 2020 10:48:06 -0500 > Subject: [PATCH] lockpagememcg > > --- > include/linux/memcontrol.h | 61 ++++++++++++++++++++++++++-- > mm/memcontrol.c | 82 +++++++------------------------------- > 2 files changed, 73 insertions(+), 70 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 20108e426f84..b4b73e375948 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -842,9 +842,64 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg); > extern bool cgroup_memory_noswap; > #endif > > -struct mem_cgroup *lock_page_memcg(struct page *page); > -void __unlock_page_memcg(struct mem_cgroup *memcg); > -void unlock_page_memcg(struct page *page); > +struct mem_cgroup *lock_page_memcg_slowpath(struct page *page, > + struct mem_cgroup *memcg); > +void unlock_page_memcg_slowpath(struct mem_cgroup *memcg); > + > +/** > + * lock_page_memcg - lock a page and memcg binding > + * @page: the page > + * > + * This function protects unlocked LRU pages from being moved to > + * another cgroup. > + * > + * It ensures lifetime of the memcg -- the caller is responsible for > + * the lifetime of the page; __unlock_page_memcg() is available when > + * @page might get freed inside the locked section. > + */ > +static inline struct mem_cgroup *lock_page_memcg(struct page *page) > +{ > + struct page *head = compound_head(page); /* rmap on tail pages */ > + struct mem_cgroup *memcg; > + > + /* > + * The RCU lock is held throughout the transaction. The fast > + * path can get away without acquiring the memcg->move_lock > + * because page moving starts with an RCU grace period. > + * > + * The RCU lock also protects the memcg from being freed when > + * the page state that is going to change is the only thing > + * preventing the page itself from being freed. E.g. writeback > + * doesn't hold a page reference and relies on PG_writeback to > + * keep off truncation, migration and so forth. > + */ > + rcu_read_lock(); > + > + if (mem_cgroup_disabled()) > + return NULL; > + > + memcg = page_memcg(head); > + if (unlikely(!memcg)) > + return NULL; > + > + if (likely(!atomic_read(&memcg->moving_account))) > + return memcg; > + > + return lock_page_memcg_slowpath(head, memcg); > +} > + > +static inline void __unlock_page_memcg(struct mem_cgroup *memcg) > +{ > + if (unlikely(memcg && memcg->move_lock_task == current)) > + unlock_page_memcg_slowpath(memcg); > + > + rcu_read_unlock(); > +} > + > +static inline void unlock_page_memcg(struct page *page) > +{ > + __unlock_page_memcg(page_memcg(compound_head(page))); > +} > > /* > * idx can be of type enum memcg_stat_item or node_stat_item. > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 69a2893a6455..9acc42388b86 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2084,49 +2084,19 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) > pr_cont(" are going to be killed due to memory.oom.group set\n"); > } > > -/** > - * lock_page_memcg - lock a page and memcg binding > - * @page: the page > - * > - * This function protects unlocked LRU pages from being moved to > - * another cgroup. > - * > - * It ensures lifetime of the returned memcg. Caller is responsible > - * for the lifetime of the page; __unlock_page_memcg() is available > - * when @page might get freed inside the locked section. > - */ > -struct mem_cgroup *lock_page_memcg(struct page *page) > +struct mem_cgroup *lock_page_memcg_slowpath(struct page *page, > + struct mem_cgroup *memcg) > { > - struct page *head = compound_head(page); /* rmap on tail pages */ > - struct mem_cgroup *memcg; > unsigned long flags; > - > - /* > - * The RCU lock is held throughout the transaction. The fast > - * path can get away without acquiring the memcg->move_lock > - * because page moving starts with an RCU grace period. > - * > - * The RCU lock also protects the memcg from being freed when > - * the page state that is going to change is the only thing > - * preventing the page itself from being freed. E.g. writeback > - * doesn't hold a page reference and relies on PG_writeback to > - * keep off truncation, migration and so forth. > - */ > - rcu_read_lock(); > - > - if (mem_cgroup_disabled()) > - return NULL; > again: > - memcg = page_memcg(head); > - if (unlikely(!memcg)) > - return NULL; > - > - if (atomic_read(&memcg->moving_account) <= 0) > - return memcg; > - > spin_lock_irqsave(&memcg->move_lock, flags); > - if (memcg != page_memcg(head)) { > + if (memcg != page_memcg(page)) { > spin_unlock_irqrestore(&memcg->move_lock, flags); > + memcg = page_memcg(page); > + if (unlikely(!memcg)) > + return NULL; > + if (!atomic_read(&memcg->moving_account)) > + return memcg; > goto again; > } > > @@ -2140,39 +2110,17 @@ struct mem_cgroup *lock_page_memcg(struct page *page) > > return memcg; > } > -EXPORT_SYMBOL(lock_page_memcg); > - > -/** > - * __unlock_page_memcg - unlock and unpin a memcg > - * @memcg: the memcg > - * > - * Unlock and unpin a memcg returned by lock_page_memcg(). > - */ > -void __unlock_page_memcg(struct mem_cgroup *memcg) > -{ > - if (memcg && memcg->move_lock_task == current) { > - unsigned long flags = memcg->move_lock_flags; > - > - memcg->move_lock_task = NULL; > - memcg->move_lock_flags = 0; > - > - spin_unlock_irqrestore(&memcg->move_lock, flags); > - } > - > - rcu_read_unlock(); > -} > +EXPORT_SYMBOL(lock_page_memcg_slowpath); > > -/** > - * unlock_page_memcg - unlock a page and memcg binding > - * @page: the page > - */ > -void unlock_page_memcg(struct page *page) > +void unlock_page_memcg_slowpath(struct mem_cgroup *memcg) > { > - struct page *head = compound_head(page); > + unsigned long flags = memcg->move_lock_flags; > > - __unlock_page_memcg(page_memcg(head)); > + memcg->move_lock_task = NULL; > + memcg->move_lock_flags = 0; > + spin_unlock_irqrestore(&memcg->move_lock, flags); > } > -EXPORT_SYMBOL(unlock_page_memcg); > +EXPORT_SYMBOL(unlock_page_memcg_slowpath); > > struct memcg_stock_pcp { > struct mem_cgroup *cached; /* this never be root cgroup */ >
-- Zhengjun Xing
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