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imf29.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf29.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712302117; a=rsa-sha256; cv=none; b=SyRA2ZSInshEaUoplGuj1QUvl5kQ+EHZmmNl8akTWvvlEbNgx3h6Ubj6hRwIWhx6iF/I9m lyT9hcBZzDwvaQjoqCsqsRxCnU75Tv+AtCfjXXQ1sYJQM7XkVviTyxSzd87pt+2Sm4FtKq qeVsv8EIMKYOdv37eEU9G2UrOFDns1I= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EFAA6FEC; Fri, 5 Apr 2024 00:29:06 -0700 (PDT) Received: from [10.57.74.169] (unknown [10.57.74.169]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4183D3F64C; Fri, 5 Apr 2024 00:28:34 -0700 (PDT) Message-ID: <9ce0ee64-d3b1-4da2-bec9-36fb3a8191d1@arm.com> Date: Fri, 5 Apr 2024 08:28:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 5/6] mm: vmscan: Avoid split during shrink_folio_list() Content-Language: en-GB To: Barry Song <21cnbao@gmail.com> Cc: Andrew Morton , David Hildenbrand , Matthew Wilcox , Huang Ying , Gao Xiang , Yu Zhao , Yang Shi , Michal Hocko , Kefeng Wang , Chris Li , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song References: <20240327144537.4165578-1-ryan.roberts@arm.com> <20240327144537.4165578-6-ryan.roberts@arm.com> <63c9caf4-3af4-4149-b3c2-e677788cb11f@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7948512000C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: wfs5hbo8g8wwimejdowpyuzgct6b967u X-HE-Tag: 1712302117-46135 X-HE-Meta: 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 7qtYKb78 3N1M8sC0XEdttjJgJsv8j9NZzLsR6gjZ0/gDbwCZFLUh/8Xzlkv7ATyCvP+YnAQZQeRV7x1NoVlHZF5+nGxMueTaXV3K/J//oZCs7w/AaaRl2NELfSjCJxbuzJKwGl9h5Le8NADW4uazu3FVPvXaUOzYB+hLHQe81P1z2QYmLEsdBT7XSRit2PytjQofz2UhTWGaA8MyCiaIfw4MaLE2VWS3Yyan5OrWQ2chMuF3hsNWHsAELPxpCWdeiE07eYrVYv2nhw5C92pAr+xuqeaRcgRb3oydG4t0rd+/6srd8PyIptzpjHKXZgOlCxketLNQZoEAoK5yGz7xLb4SculW1YXU4mbaaSIN1KAvwWpcz/lRDR90= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 05/04/2024 05:06, Barry Song wrote: > On Wed, Apr 3, 2024 at 2:10 AM Ryan Roberts wrote: >> >> On 28/03/2024 08:18, Barry Song wrote: >>> On Thu, Mar 28, 2024 at 3:45 AM Ryan Roberts wrote: >>>> >>>> Now that swap supports storing all mTHP sizes, avoid splitting large >>>> folios before swap-out. This benefits performance of the swap-out path >>>> by eliding split_folio_to_list(), which is expensive, and also sets us >>>> up for swapping in large folios in a future series. >>>> >>>> If the folio is partially mapped, we continue to split it since we want >>>> to avoid the extra IO overhead and storage of writing out pages >>>> uneccessarily. >>>> >>>> Reviewed-by: David Hildenbrand >>>> Reviewed-by: Barry Song >>>> Signed-off-by: Ryan Roberts >>>> --- >>>> mm/vmscan.c | 9 +++++---- >>>> 1 file changed, 5 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>> index 00adaf1cb2c3..293120fe54f3 100644 >>>> --- a/mm/vmscan.c >>>> +++ b/mm/vmscan.c >>>> @@ -1223,11 +1223,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, >>>> if (!can_split_folio(folio, NULL)) >>>> goto activate_locked; >>>> /* >>>> - * Split folios without a PMD map right >>>> - * away. Chances are some or all of the >>>> - * tail pages can be freed without IO. >>>> + * Split partially mapped folios right >>>> + * away. We can free the unmapped pages >>>> + * without IO. >>>> */ >>>> - if (!folio_entire_mapcount(folio) && >>>> + if (data_race(!list_empty( >>>> + &folio->_deferred_list)) && >>>> split_folio_to_list(folio, >>>> folio_list)) >>>> goto activate_locked; >>> >>> Hi Ryan, >>> >>> Sorry for bringing up another minor issue at this late stage. >> >> No problem - I'd rather take a bit longer and get it right, rather than rush it >> and get it wrong! >> >>> >>> During the debugging of thp counter patch v2, I noticed the discrepancy between >>> THP_SWPOUT_FALLBACK and THP_SWPOUT. >>> >>> Should we make adjustments to the counter? >> >> Yes, agreed; we want to be consistent here with all the other existing THP >> counters; they only refer to PMD-sized THP. I'll make the change for the next >> version. >> >> I guess we will eventually want equivalent counters for per-size mTHP using the >> framework you are adding. > > Hi Ryan, > > Today, I created counters for per-order SWPOUT and SWPOUT_FALLBACK. > I'd appreciate any > suggestions you might have before I submit this as patch 2/2 of my > mTHP counters series. Amazing - this is going to be very useful! > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index cc13fa14aa32..762a6d8759b9 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -267,6 +267,8 @@ unsigned long thp_vma_allowable_orders(struct > vm_area_struct *vma, > enum thp_stat_item { > THP_STAT_ANON_ALLOC, > THP_STAT_ANON_ALLOC_FALLBACK, > + THP_STAT_ANON_SWPOUT, > + THP_STAT_ANON_SWPOUT_FALLBACK, > __THP_STAT_COUNT > }; > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index e704b4408181..7f2b5d2852cc 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -554,10 +554,14 @@ static struct kobj_attribute _name##_attr = > __ATTR_RO(_name) > > THP_STATE_ATTR(anon_alloc, THP_STAT_ANON_ALLOC); > THP_STATE_ATTR(anon_alloc_fallback, THP_STAT_ANON_ALLOC_FALLBACK); > +THP_STATE_ATTR(anon_swpout, THP_STAT_ANON_SWPOUT); > +THP_STATE_ATTR(anon_swpout_fallback, THP_STAT_ANON_SWPOUT_FALLBACK); > > static struct attribute *stats_attrs[] = { > &anon_alloc_attr.attr, > &anon_alloc_fallback_attr.attr, > + &anon_swpout_attr.attr, > + &anon_swpout_fallback_attr.attr, > NULL, > }; > > diff --git a/mm/page_io.c b/mm/page_io.c > index a9a7c236aecc..be4f822b39f8 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -212,13 +212,16 @@ int swap_writepage(struct page *page, struct > writeback_control *wbc) > > static inline void count_swpout_vm_event(struct folio *folio) > { > + long nr_pages = folio_nr_pages(folio); > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > if (unlikely(folio_test_pmd_mappable(folio))) { > count_memcg_folio_events(folio, THP_SWPOUT, 1); > count_vm_event(THP_SWPOUT); > } > + if (nr_pages > 0 && nr_pages <= HPAGE_PMD_NR) The guard is a bit ugly; I wonder if we should at least check that order is in bounds in count_thp_state(), since all callers could benefit? Then we only have to care about the nr_pages > 0 condition here. Just a thought... > + count_thp_state(folio_order(folio), THP_STAT_ANON_SWPOUT); So you're counting THPs, not pages; I agree with that approach. > #endif > - count_vm_events(PSWPOUT, folio_nr_pages(folio)); > + count_vm_events(PSWPOUT, nr_pages); > } > > #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ffc4553c8615..b7c5fbd830b6 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1247,6 +1247,10 @@ static unsigned int shrink_folio_list(struct > list_head *folio_list, > count_vm_event( > THP_SWPOUT_FALLBACK); > } > + if (nr_pages > 0 && nr_pages > <= HPAGE_PMD_NR) > + > count_thp_state(folio_order(folio), > + > THP_STAT_ANON_SWPOUT_FALLBACK); > + > #endif > if (!add_to_swap(folio)) > goto activate_locked_split; > > > Thanks > Barry