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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AE0F0CD6E51 for ; Sun, 31 May 2026 07:31:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D51AC6B010D; Sun, 31 May 2026 03:31:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D03096B010E; Sun, 31 May 2026 03:31:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BF0FC6B010F; Sun, 31 May 2026 03:31:23 -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 B19316B010D for ; Sun, 31 May 2026 03:31:23 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 6205B1C0628 for ; Sun, 31 May 2026 07:31:23 +0000 (UTC) X-FDA: 84826894446.04.2DE6E3D Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) by imf05.hostedemail.com (Postfix) with ESMTP id 98C4710000A for ; Sun, 31 May 2026 07:31:21 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="GLxC/+IQ"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780212681; 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=ygMusJ4OhxFWYgfdJFdjk6JjCc/P5Yv4lLsq+6asc2I=; b=O6TVcYH2Gb8s7CmkZXQ4BNVCGt/DNm87XhQJsiXtkhi7Wl6SCQ6H42VlfJWlBkdHgLYpR9 76NYdZePY1mzICNa0t/94rCwCKnLQckmdUJp9S5PYBybHnoNlmprzigHEvor2ZPJ60Fg2S tXRs5Fwydzanq789pixjkUqVqPmCtH4= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="GLxC/+IQ"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1780212681; a=rsa-sha256; cv=none; b=HlfulDEmNaiN2AWHHawK0cMFWK1EoECaE0i+gTp72MN/HhFu8/3+AAkJKXuI4eGhZXZJcF cdl0jV2uxEiH6EPmWebR4L6vcV7H15c0nfgFuNi8F2ZSsk0MnQfra4T0JgH1yXI2MGd38t 3WXSXg1kIoY4PNJQDA0kFbPJXsd33K0= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780212678; h=from:from: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=ygMusJ4OhxFWYgfdJFdjk6JjCc/P5Yv4lLsq+6asc2I=; b=GLxC/+IQoaYnWqMbHdZqSraF09cYIqx1TkB97Iseulqg7tgBNUbFR46llX5lxy/ymBtQqv ta1xf7DjhgeW2OqmHLXsTMw/0Ulf6309h0NH56ha+aGc/AaAGZdFlMvFzL8F4qoKgQF23n J+dGGm1xnDWnqudtQmP4PWNJD6sQVHo= From: Lance Yang To: npache@redhat.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com, usama.arif@linux.dev Subject: Re: [PATCH mm-unstable v18 12/14] mm/khugepaged: avoid unnecessary mTHP collapse attempts Date: Sun, 31 May 2026 15:31:02 +0800 Message-Id: <20260531073102.20318-1-lance.yang@linux.dev> In-Reply-To: <20260522150009.121603-13-npache@redhat.com> References: <20260522150009.121603-13-npache@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 98C4710000A X-Stat-Signature: 8ymiqdxu1bhtparj1zo8rqgz8kz4xg3j X-Rspam-User: X-HE-Tag: 1780212681-535980 X-HE-Meta: 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 cbXwv8tO C121RuKaUJByZ5pCaHwo6KYm8rRBdDihoxd6ICZZJHBa0gu1I+EXZLZxEGPslgpy+dfvSsjbVGqJB+LhDsdQikAt1GqxahbEh5A587UdH4ZJ93XEOpEah4griSxNxNROVs5mYngMjMl+s6tPr+uoOsHZnDGJdDIYwfTKt+ZG4CKoU8XESB7DV0UZrtjyk0e9TF7yADOi8eVSghN6JrDD+jLO8NYFfwZR6Ii3kxPdSlU2yWZWhNEDCicootd2ElIsfZabbLGNYsPe46bJ4M4G555UbwaAs6CymOBpOlK42ZjfJ3J3OaQUbHZ9t49F7hzoPqUmGaPYatTCUec33sp/B/0hPuddk8+5ItuAaGiH6zIVgFCk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 22, 2026 at 09:00:07AM -0600, Nico Pache wrote: >There are cases where, if an attempted collapse fails, all subsequent >orders are guaranteed to also fail. Avoid these collapse attempts by >bailing out early. > >Reviewed-by: Lorenzo Stoakes >Acked-by: Usama Arif >Acked-by: David Hildenbrand (Arm) >Signed-off-by: Nico Pache >--- > mm/khugepaged.c | 24 +++++++++++++++++++++++- > 1 file changed, 23 insertions(+), 1 deletion(-) > >diff --git a/mm/khugepaged.c b/mm/khugepaged.c >index d3d7db8be26c..15b7298bc225 100644 >--- a/mm/khugepaged.c >+++ b/mm/khugepaged.c >@@ -1535,9 +1535,31 @@ static int mthp_collapse(struct mm_struct *mm, struct vm_area_struct *vma, > collapse_address = address + offset * PAGE_SIZE; > ret = collapse_huge_page(mm, collapse_address, referenced, > unmapped, cc, order); >- if (ret == SCAN_SUCCEED) { >+ >+ switch (ret) { >+ /* Cases where we continue to next collapse candidate */ >+ case SCAN_SUCCEED: > collapsed += nr_ptes; >+ fallthrough; >+ case SCAN_PTE_MAPPED_HUGEPAGE: > continue; >+ /* Cases where lower orders might still succeed */ >+ case SCAN_LACK_REFERENCED_PAGE: >+ case SCAN_EXCEED_NONE_PTE: >+ case SCAN_EXCEED_SWAP_PTE: >+ case SCAN_EXCEED_SHARED_PTE: >+ case SCAN_PAGE_LOCK: >+ case SCAN_PAGE_COUNT: >+ case SCAN_PAGE_NULL: >+ case SCAN_DEL_PAGE_LRU: >+ case SCAN_PTE_NON_PRESENT: >+ case SCAN_PTE_UFFD_WP: >+ case SCAN_ALLOC_HUGE_PAGE_FAIL: Nit: shouldn't SCAN_CGROUP_CHARGE_FAIL go with SCAN_ALLOC_HUGE_PAGE_FAIL here? If charging the current order fails, a smaller order might still fit :) Cheers, Lance >+ case SCAN_PAGE_LAZYFREE: >+ goto next_order; >+ /* Cases where no further collapse is possible */ >+ default: >+ return collapsed; > } > } > >-- >2.54.0 > >