From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7E73C4828D for ; Mon, 5 Feb 2024 06:42:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C26A8D0001; Mon, 5 Feb 2024 01:42:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 24BC86B0075; Mon, 5 Feb 2024 01:42:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0EE388D0001; Mon, 5 Feb 2024 01:42:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id EEA766B0074 for ; Mon, 5 Feb 2024 01:42:49 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id B7CE414079D for ; Mon, 5 Feb 2024 06:42:49 +0000 (UTC) X-FDA: 81756807258.29.0C5C62F Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf23.hostedemail.com (Postfix) with ESMTP id 5D6F7140002 for ; Mon, 5 Feb 2024 06:42:45 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf23.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707115368; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9OhdOMJJY2BfwUroTF+DvDFCymZGP7W3hWhOkJqRWPk=; b=F7MxEpXZSDacx7FOdQANRxMzV8um8Vr6SfgmdptBuuD6rLwXMCPUsiE5oYOdYaSFLKHIvS fjpQFa5rJKteAsk8w45zF/ie4RvM+nELVCK6XtXqOmHE71thahJFxaZNA0ZECo8Bfj6pio gJSnxzZPLQ7ilZGUkEkF7Gpw1yIPTfE= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf23.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707115368; a=rsa-sha256; cv=none; b=C3i5h4qOE8o7h+95wxSDuiPx3hd5UyykqRwPUEjxKYinptJwPugex41KmWQU/wbHq5tgp2 Ljn5QsoIOjyxQF0lY814h89gULMYQ6wy6Tbft4riCDk/WuMNwbcV3DbJHAR8vnQLmkG+la mIy4GpICdd5Ukxb+1Kz064Mix6iNn8A= Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4TSxc316R8zsSh3; Mon, 5 Feb 2024 14:41:23 +0800 (CST) Received: from kwepemm600020.china.huawei.com (unknown [7.193.23.147]) by mail.maildlp.com (Postfix) with ESMTPS id 82FC7140153; Mon, 5 Feb 2024 14:42:41 +0800 (CST) Received: from [10.174.179.160] (10.174.179.160) by kwepemm600020.china.huawei.com (7.193.23.147) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 5 Feb 2024 14:42:40 +0800 Message-ID: <6683b9ea-469d-8c8f-abf6-eb21a6cae8b9@huawei.com> Date: Mon, 5 Feb 2024 14:42:39 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH] filemap: avoid unnecessary major faults in filemap_fault() Content-Language: en-US To: "Huang, Ying" CC: , , , , , , , , , References: <20240204093526.212636-1-zhangpeng362@huawei.com> <874jen4o43.fsf@yhuang6-desk2.ccr.corp.intel.com> From: "zhangpeng (AS)" In-Reply-To: <874jen4o43.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.160] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm600020.china.huawei.com (7.193.23.147) X-Rspamd-Queue-Id: 5D6F7140002 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 8zxci646q3cyhqo4hotxeybog3nz7a49 X-HE-Tag: 1707115365-247942 X-HE-Meta: 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 mUzNqX3K E6wvBcvpTlDeTZ/N2lriimWgAZjFSkQEGmAGtJ0Bfs4Gw+FKiXizk4clvHFxy+8KPJUWRBkJiLxqRuubPV4YKKaq6jWMqOE1ru9cnEVESEluMKOdJD+Q4OOWfTMTQIWU/TnnYTd7IsrlKH1kWbl2VPisUT4IjyUTW60L4j3eeCpsOKE6/POrLgJtO1LglFiUeodRrs9WzmIi4VOcuaBgqJaE4bQcR1i7yGns79/sXkyZVd1e3l7ZamfROcMSpPGAyReG/dm0T5+6SaTUEYpNzegHgkKKnN+j0S+Dqqw7KDo08C+Or/aqJQNKCE75n6VWXVq5z9RGTDZZEX9o= 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 2024/2/5 10:54, Huang, Ying wrote: > Peng Zhang writes: >> From: ZhangPeng >> >> The major fault occurred when using mlockall(MCL_CURRENT | MCL_FUTURE) >> in application, which leading to an unexpected performance issue[1]. >> >> This caused by temporarily cleared PTE during a read/modify/write update >> of the PTE, eg, do_numa_page()/change_pte_range(). >> >> For the data segment of the user-mode program, the global variable area >> is a private mapping. After the pagecache is loaded, the private anonymous >> page is generated after the COW is triggered. Mlockall can lock COW pages >> (anonymous pages), but the original file pages cannot be locked and may >> be reclaimed. If the global variable (private anon page) is accessed when >> vmf->pte is zeroed in numa fault, a file page fault will be triggered. >> >> At this time, the original private file page may have been reclaimed. >> If the page cache is not available at this time, a major fault will be >> triggered and the file will be read, causing additional overhead. >> >> Fix this by rechecking the PTE without acquiring PTL in filemap_fault() >> before triggering a major fault. >> >> Testing file anonymous page read and write page fault performance in ext4 >> and ramdisk using will-it-scale[2] on a x86 physical machine. The data >> is the average change compared with the mainline after the patch is >> applied. The test results are within the range of fluctuation, and there >> is no obvious difference. The test results are as follows: >> processes processes_idle threads threads_idle >> ext4 file write: -1.14% -0.08% -1.87% 0.13% >> ext4 file read: 0.03% -0.65% -0.51% -0.08% >> ramdisk file write: -1.21% -0.21% -1.12% 0.11% >> ramdisk file read: 0.00% -0.68% -0.33% -0.02% > IIUC, this is the regression test results. Right? Can you also show > improvement test results to justify the change? Sure, I'll add the improvement test results as follows: processes processes_idle threads threads_idle ext4 private file write: -1.14% -0.08% -1.87% 0.13% ext4 shared file write: 0.14% -0.53% 2.88% -0.77% ext4 private file read: 0.03% -0.65% -0.51% -0.08% tmpfs private file write: -0.34% -0.11% 0.20% 0.15% tmpfs shared file write: 0.96% 0.10% 2.78% -0.34% ramdisk private file write: -1.21% -0.21% -1.12% 0.11% ramdisk private file read: 0.00% -0.68% -0.33% -0.02% > > -- > Best Regards, > Huang, Ying > >> [1] https://lore.kernel.org/linux-mm/9e62fd9a-bee0-52bf-50a7-498fa17434ee@huawei.com/ >> [2] https://github.com/antonblanchard/will-it-scale/ >> >> Suggested-by: "Huang, Ying" >> Suggested-by: Yin Fengwei >> Signed-off-by: ZhangPeng >> Signed-off-by: Kefeng Wang >> --- >> RFC->v1: >> - Add error handling when ptep == NULL per Huang, Ying and Matthew Wilcox >> - Check the PTE without acquiring PTL in filemap_fault(), suggested by >> Huang, Ying and Yin Fengwei >> - Add pmd_none() check before PTE map >> - Update commit message and add performance test information >> >> mm/filemap.c | 18 ++++++++++++++++++ >> 1 file changed, 18 insertions(+) >> >> diff --git a/mm/filemap.c b/mm/filemap.c >> index 142864338ca4..b29cdeb6a03b 100644 >> --- a/mm/filemap.c >> +++ b/mm/filemap.c >> @@ -3238,6 +3238,24 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) >> mapping_locked = true; >> } >> } else { >> + if (!pmd_none(*vmf->pmd)) { >> + pte_t *ptep; >> + >> + ptep = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd, >> + vmf->address, &vmf->ptl); >> + if (unlikely(!ptep)) >> + return VM_FAULT_NOPAGE; >> + /* >> + * Recheck pte as the pte can be cleared temporarily >> + * during a read/modify/write update. >> + */ >> + if (unlikely(!pte_none(ptep_get_lockless(ptep)))) >> + ret = VM_FAULT_NOPAGE; >> + pte_unmap(ptep); >> + if (unlikely(ret)) >> + return ret; >> + } >> + >> /* No page in the page cache at all */ >> count_vm_event(PGMAJFAULT); >> count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); -- Best Regards, Peng