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 X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FE0BC2D0F3 for ; Wed, 1 Apr 2020 06:03:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C1D752077D for ; Wed, 1 Apr 2020 06:03:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="YfALPzGA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1D752077D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex-team.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5AFE66B000C; Wed, 1 Apr 2020 02:03:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 560A26B000D; Wed, 1 Apr 2020 02:03:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4017C6B006C; Wed, 1 Apr 2020 02:03:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0185.hostedemail.com [216.40.44.185]) by kanga.kvack.org (Postfix) with ESMTP id 24E9D6B000C for ; Wed, 1 Apr 2020 02:03:51 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C69808248076 for ; Wed, 1 Apr 2020 06:03:50 +0000 (UTC) X-FDA: 76658245020.15.jeans02_44b768e31e62 X-HE-Tag: jeans02_44b768e31e62 X-Filterd-Recvd-Size: 5495 Received: from forwardcorp1j.mail.yandex.net (forwardcorp1j.mail.yandex.net [5.45.199.163]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Wed, 1 Apr 2020 06:03:49 +0000 (UTC) Received: from mxbackcorp1j.mail.yandex.net (mxbackcorp1j.mail.yandex.net [IPv6:2a02:6b8:0:1619::162]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 9CB872E15AB; Wed, 1 Apr 2020 09:03:46 +0300 (MSK) Received: from myt5-70c90f7d6d7d.qloud-c.yandex.net (myt5-70c90f7d6d7d.qloud-c.yandex.net [2a02:6b8:c12:3e2c:0:640:70c9:f7d]) by mxbackcorp1j.mail.yandex.net (mxbackcorp/Yandex) with ESMTP id 5s7A5tV1Tc-3jZeji0t; Wed, 01 Apr 2020 09:03:46 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1585721026; bh=1bAHvSB3kmRgmi7tuFuA6Fe/PqgZGvIRR5VswNBqy+Q=; h=In-Reply-To:Message-ID:From:Date:References:To:Subject:Cc; b=YfALPzGAC6zjrqj4KLwLgQrUp2Jgykdgm5P/IsAz49/3PlbuZQCVHf0jt3Y8IDSWG 2W/G0oynp9cNGWT37lf1aWhTPshOpu2Va5aUs06ssAtNvEMpnqa7bazieO2vVAMD3A upWnmJjWk5+mxuYs7aOHiICf/FtpjVsj5vJwYRis= Authentication-Results: mxbackcorp1j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from unknown (unknown [2a02:6b8:b080:7613::1:5]) by myt5-70c90f7d6d7d.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id zG2YiQjTrL-3jWWQ0xO; Wed, 01 Apr 2020 09:03:45 +0300 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) Subject: Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrea Arcangeli , "Kirill A . Shutemov" , Zi Yan , Vlastimil Babka , Alexey Dobriyan , Michal Hocko , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Yang Shi References: <20200331085604.1260162-1-ying.huang@intel.com> <49386753-5984-f708-4153-e9c6de632439@yandex-team.ru> <87mu7whr88.fsf@yhuang-dev.intel.com> From: Konstantin Khlebnikov Message-ID: Date: Wed, 1 Apr 2020 09:03:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <87mu7whr88.fsf@yhuang-dev.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: quoted-printable 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: On 01/04/2020 05.31, Huang, Ying wrote: > Konstantin Khlebnikov writes: >=20 >> On 31/03/2020 11.56, Huang, Ying wrote: >>> From: Huang Ying >>> >>> Now, when read /proc/PID/smaps, the PMD migration entry in page table= is simply >>> ignored. To improve the accuracy of /proc/PID/smaps, its parsing and= processing >>> is added. >>> >>> Signed-off-by: "Huang, Ying" >>> Cc: Andrea Arcangeli >>> Cc: Kirill A. Shutemov >>> Cc: Zi Yan >>> Cc: Vlastimil Babka >>> Cc: Alexey Dobriyan >>> Cc: Michal Hocko >>> Cc: Konstantin Khlebnikov >>> Cc: "J=C3=A9r=C3=B4me Glisse" >>> Cc: Yang Shi >>> --- >>> fs/proc/task_mmu.c | 16 ++++++++++++---- >>> 1 file changed, 12 insertions(+), 4 deletions(-) >>> >>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >>> index 8d382d4ec067..b5b3aef8cb3b 100644 >>> --- a/fs/proc/task_mmu.c >>> +++ b/fs/proc/task_mmu.c >>> @@ -548,8 +548,17 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned= long addr, >>> bool locked =3D !!(vma->vm_flags & VM_LOCKED); >>> struct page *page; >> >> struct page *page =3D NULL; >=20 > Looks good. Will do this in the next version. >=20 >>> - /* FOLL_DUMP will return -EFAULT on huge zero page */ >>> - page =3D follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); >>> + if (pmd_present(*pmd)) { >>> + /* FOLL_DUMP will return -EFAULT on huge zero page */ >>> + page =3D follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); >>> + } else if (unlikely(is_swap_pmd(*pmd))) { >>> + swp_entry_t entry =3D pmd_to_swp_entry(*pmd); >>> + >>> + VM_BUG_ON(!is_migration_entry(entry)); >>> + page =3D migration_entry_to_page(entry); >> >> if (is_migration_entry(entry)) >> page =3D migration_entry_to_page(entry); >> >> Seems safer and doesn't add much code. >=20 > With this, we lose an opportunity to capture some bugs during debugging= . > Right? You can keep VM_BUG_ON or VM_WARN_ON_ONCE Off-by-page in statistics isn't a big deal and not a good reason to crash= (even debug) kernel. But for normal build should use safe behaviour if this isn't hard. >=20 > Best Regards, > Huang, Ying >=20 >>> + } else { >>> + return; >>> + } >>> if (IS_ERR_OR_NULL(page)) >>> return; >>> if (PageAnon(page)) >>> @@ -578,8 +587,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned l= ong addr, unsigned long end, >>> ptl =3D pmd_trans_huge_lock(pmd, vma); >>> if (ptl) { >>> - if (pmd_present(*pmd)) >>> - smaps_pmd_entry(pmd, addr, walk); >>> + smaps_pmd_entry(pmd, addr, walk); >>> spin_unlock(ptl); >>> goto out; >>> } >>>