Messages in this thread | | | Subject | Re: [PATCH 1/2] mm: swap: make page_evictable() inline | From | Yang Shi <> | Date | Fri, 13 Mar 2020 12:46:46 -0700 |
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On 3/13/20 12:33 PM, Shakeel Butt wrote: > On Fri, Mar 13, 2020 at 11:34 AM Yang Shi <yang.shi@linux.alibaba.com> wrote: >> When backporting commit 9c4e6b1a7027 ("mm, mlock, vmscan: no more >> skipping pagevecs") to our 4.9 kernel, our test bench noticed around 10% >> down with a couple of vm-scalability's test cases (lru-file-readonce, >> lru-file-readtwice and lru-file-mmap-read). I didn't see that much down >> on my VM (32c-64g-2nodes). It might be caused by the test configuration, >> which is 32c-256g with NUMA disabled and the tests were run in root memcg, >> so the tests actually stress only one inactive and active lru. It >> sounds not very usual in mordern production environment. >> >> That commit did two major changes: >> 1. Call page_evictable() >> 2. Use smp_mb to force the PG_lru set visible >> >> It looks they contribute the most overhead. The page_evictable() is a >> function which does function prologue and epilogue, and that was used by >> page reclaim path only. However, lru add is a very hot path, so it >> sounds better to make it inline. However, it calls page_mapping() which >> is not inlined either, but the disassemble shows it doesn't do push and >> pop operations and it sounds not very straightforward to inline it. >> >> Other than this, it sounds smp_mb() is not necessary for x86 since >> SetPageLRU is atomic which enforces memory barrier already, replace it >> with smp_mb__after_atomic() in the following patch. >> >> With the two fixes applied, the tests can get back around 5% on that >> test bench and get back normal on my VM. Since the test bench >> configuration is not that usual and I also saw around 6% up on the >> latest upstream, so it sounds good enough IMHO. >> >> The below is test data (lru-file-readtwice throughput) against the v5.6-rc4: >> mainline w/ inline fix >> 150MB 154MB >> > What is the test setup for the above experiment? I would like to get a repro.
Just startup a VM with two nodes, then run case-lru-file-readtwice or case-lru-file-readonce in vm-scalability in root memcg or with memcg disabled. Then get the average throughput (dd result) from the test. Our test bench uses the script from lkp, but I just ran it manually. Single node VM should be more obvious showed in my test.
> >> With this patch the throughput gets 2.67% up. The data with using >> smp_mb__after_atomic() is showed in the following patch. >> >> Fixes: 9c4e6b1a7027 ("mm, mlock, vmscan: no more skipping pagevecs") >> Cc: Shakeel Butt <shakeelb@google.com> >> Cc: Vlastimil Babka <vbabka@suse.cz> >> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> >> --- >> include/linux/swap.h | 24 +++++++++++++++++++++++- >> mm/vmscan.c | 23 ----------------------- >> 2 files changed, 23 insertions(+), 24 deletions(-) >> >> diff --git a/include/linux/swap.h b/include/linux/swap.h >> index 1e99f7a..297eb66 100644 >> --- a/include/linux/swap.h >> +++ b/include/linux/swap.h >> @@ -374,7 +374,29 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem, >> #define node_reclaim_mode 0 >> #endif >> >> -extern int page_evictable(struct page *page); >> +/* >> + * page_evictable - test whether a page is evictable >> + * @page: the page to test >> + * >> + * Test whether page is evictable--i.e., should be placed on active/inactive >> + * lists vs unevictable list. >> + * >> + * Reasons page might not be evictable: >> + * (1) page's mapping marked unevictable >> + * (2) page is part of an mlocked VMA >> + * >> + */ >> +static inline int page_evictable(struct page *page) >> +{ >> + int ret; >> + >> + /* Prevent address_space of inode and swap cache from being freed */ >> + rcu_read_lock(); >> + ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); >> + rcu_read_unlock(); >> + return ret; >> +} >> + >> extern void check_move_unevictable_pages(struct pagevec *pvec); >> >> extern int kswapd_run(int nid); >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 8763705..855c395 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -4277,29 +4277,6 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) >> } >> #endif >> >> -/* >> - * page_evictable - test whether a page is evictable >> - * @page: the page to test >> - * >> - * Test whether page is evictable--i.e., should be placed on active/inactive >> - * lists vs unevictable list. >> - * >> - * Reasons page might not be evictable: >> - * (1) page's mapping marked unevictable >> - * (2) page is part of an mlocked VMA >> - * >> - */ >> -int page_evictable(struct page *page) >> -{ >> - int ret; >> - >> - /* Prevent address_space of inode and swap cache from being freed */ >> - rcu_read_lock(); >> - ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); >> - rcu_read_unlock(); >> - return ret; >> -} >> - >> /** >> * check_move_unevictable_pages - check pages for evictability and move to >> * appropriate zone lru list >> -- >> 1.8.3.1 >>
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