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 15ADBC369CB for ; Tue, 29 Apr 2025 06:53:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0AA986B0008; Tue, 29 Apr 2025 02:53:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 05A3C6B000A; Tue, 29 Apr 2025 02:53:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E8A686B000C; Tue, 29 Apr 2025 02:53:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id C9E936B0008 for ; Tue, 29 Apr 2025 02:53:43 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id D81861211C5 for ; Tue, 29 Apr 2025 06:53:44 +0000 (UTC) X-FDA: 83386165968.23.5B3A2AF Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) by imf01.hostedemail.com (Postfix) with ESMTP id CB0014000B for ; Tue, 29 Apr 2025 06:53:41 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=yje6yyeq; dmarc=pass (policy=none) header.from=linux.alibaba.com; spf=pass (imf01.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.99 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1745909623; a=rsa-sha256; cv=none; b=12FftQA+ZEGKi17SOyNcCdOTJZ6l1lx1IUgf2sIJsm/otYxIoMFrdLl3rqPXOtL0RnNmpC UiWPsJmsT91IqfqQNMBJ6sceiB2TU4UFM+K+Z0D71szEclOk9grpQTHm9ro0/QzB5IbPLR Mg5adGpqFibxmCfLOVwGc1QIY0DM/XU= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=yje6yyeq; dmarc=pass (policy=none) header.from=linux.alibaba.com; spf=pass (imf01.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.99 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1745909623; 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:dkim-signature; bh=zKUAIH8fJv5MObC6iQu8Od+JSaRaIcL2RN27u9jfiXM=; b=7nStKFoGRdi9fJApTSklDNT0gFFu1Nw4kBot7+kM9WbNvkJM04lhb2ny6hmGBPats4yAd5 9nKa5Ia4g8UF5Mvr3EspJQApRjJzNcWQRj+HPpkZTcb8/L/R2iyHXuL3+x+st53F4xKM+P /rMfVnATmHqvoxHBdSO/1dL/5Evuv0s= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1745909618; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=zKUAIH8fJv5MObC6iQu8Od+JSaRaIcL2RN27u9jfiXM=; b=yje6yyeqqw5s2yl7A2DpzghaEh1T+FPmegbZJ1JfKgop7dVqQkwozqY0CC6uY02sIhgRNiD48D6cXimfRQTUWJkyP05RikyZHJ+acMWgh7SW2kxlrKio0uIGfm/bwtDmVRPcUy2aSlGAF19TWSmVUEOpsD8ySFgTAyMfy38eu7U= Received: from 30.74.146.169(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WYcp48f_1745909615 cluster:ay36) by smtp.aliyun-inc.com; Tue, 29 Apr 2025 14:53:36 +0800 Message-ID: Date: Tue, 29 Apr 2025 14:53:35 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 08/12] khugepaged: skip collapsing mTHP to smaller orders To: Nico Pache Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org References: <20250417000238.74567-1-npache@redhat.com> <20250417000238.74567-9-npache@redhat.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: CB0014000B X-Stat-Signature: agrupqis8dhbp5aphmst383sszmnkdxk X-Rspam-User: X-HE-Tag: 1745909621-362709 X-HE-Meta: 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 GNUewNiD 8ltg01aZsz3ihW6/HYjWr7jJLW/ETmERNc6htaGHJwOx2CSa/5/IXIc9/YwRH7N26rNOKDsVLh95lp2sVulbgkSbyuI/grdiyk9CqIADN/FdZQ5qBnGD+pod+Qje8IMK3cCXpq6a7H9vfFLw+V6IXPgiS/UwgTeHDM9Yp1r5EZlB9IeqzoVvsp2OV2gR1XxPXFUH4L6PyOwCzLOJkFJfH4VgUO6eiVYBQhaBRzzPn/lWYBddd7Ziwb5W7fRApxU8QkT/YHkqE4463jxg7zqsu1Gafzhv7joJ+WGVU+EobmAkoWJPsCoKxXeOrC29MB2ETBah8pIi/jPaWRx05mZZflbF4G4NTikFnIyvgB26PmiPgHxwIG7hvQuCt/gqio6nq+gNQUcaZzrCgVPtRIaHGsQMmLnFj9Ky9DiaCBaR3SgM3YjCgnwd1Krh6ILpd0tUnPeZpgJCuAz6c2wcFsySf0u0cqjJMUxMDDjNu 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 2025/4/28 23:44, Nico Pache wrote: > On Thu, Apr 24, 2025 at 1:49 AM Baolin Wang > wrote: >> >> >> >> On 2025/4/17 08:02, Nico Pache wrote: >>> khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in >>> some pages being unmapped. Skip these cases until we have a way to check >>> if its ok to collapse to a smaller mTHP size (like in the case of a >>> partially mapped folio). >>> >>> This patch is inspired by Dev Jain's work on khugepaged mTHP support [1]. >>> >>> [1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ >>> >>> Co-developed-by: Dev Jain >>> Signed-off-by: Dev Jain >>> Signed-off-by: Nico Pache >>> --- >>> mm/khugepaged.c | 7 ++++++- >>> 1 file changed, 6 insertions(+), 1 deletion(-) >>> >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index ece39fd71fe6..383aff12cd43 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -625,7 +625,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, >>> folio = page_folio(page); >>> VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); >>> >>> - /* See hpage_collapse_scan_pmd(). */ >>> + if (order != HPAGE_PMD_ORDER && folio_order(folio) >= order) { >>> + result = SCAN_PTE_MAPPED_HUGEPAGE; >>> + goto out; >>> + } >> >> Should we also add this check in hpage_collapse_scan_pmd() to abort the >> scan early? > No I dont think so, we can't abort there because we dont know the > attempted collapse order, and we dont want to miss potential mTHP > collapses (by bailing out early and not populating the bitmap). OK. That makes sense.