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 C7119CD5BD1 for ; Sun, 31 May 2026 07:19:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F3BD46B010B; Sun, 31 May 2026 03:19:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EC6046B010C; Sun, 31 May 2026 03:19:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D8DB66B010D; Sun, 31 May 2026 03:19:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id C20D76B010B for ; Sun, 31 May 2026 03:19:24 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5655A1C06D9 for ; Sun, 31 May 2026 07:19:24 +0000 (UTC) X-FDA: 84826864248.28.DF4722F Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf23.hostedemail.com (Postfix) with ESMTP id 8B2D1140006 for ; Sun, 31 May 2026 07:19:22 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="OKYxp2/e"; spf=pass (imf23.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780211962; 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=UgyOMSo1NQT9NR/s9Gmh5C++kaNJthsUpAzUGUjKh8k=; b=1YrOKIhGkQalA86E0jo9RrgzQekMU2rOtdraWYERGT/pTRsX24OUDqyi6Gp5iciPVRHWf1 WGoIdCsHakn8Zv424dqBzlt4X3VhG2/+3gzm9keIbRbbG5nkU3ILJwjoQDu+s02A5PwHFX ES/YThyy4Lv3qIe0J/2C+0T4/OWmwn0= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="OKYxp2/e"; spf=pass (imf23.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1780211962; a=rsa-sha256; cv=none; b=yO3bYkN0/0/vFXWUSVJ6SJSS4AHB4J1Zi250MIYUDXStoKfUpx8IM3A2PtUuKFt8yVy3wi OKj+9Rawv5SVdEGTDTCoDEOAuPS65EaS6eYno/Jmgp6YXhvRNY8ICN+ZlN/W1kURxjIabL Fxt8uYia4zFa9QAxB+XG7mTBGVcRbcs= 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=1780211958; 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=UgyOMSo1NQT9NR/s9Gmh5C++kaNJthsUpAzUGUjKh8k=; b=OKYxp2/euq94yW/BPlLJPwdiYfRQcuT145cwocxP1tMXDQnxVH8DFOnodfv1FPZXMlXLCc kRTYcgDt2gUggNPJiWjwTB5Smh2j0coJATntxq/OKgA9TmbAefd+z7fbWApU/qd8xKAYxI SMqIEnb+vlsE2yUpzPce/xXrgmk12Tc= 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 Subject: Re: [PATCH mm-unstable v18 11/14] mm/khugepaged: Introduce mTHP collapse support Date: Sun, 31 May 2026 15:18:45 +0800 Message-Id: <20260531071845.10875-1-lance.yang@linux.dev> In-Reply-To: <20260522150009.121603-12-npache@redhat.com> References: <20260522150009.121603-12-npache@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 68bds6qyi1mxxx8n3hqt41s9k4tht1qb X-Rspamd-Queue-Id: 8B2D1140006 X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1780211962-612759 X-HE-Meta: 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 /aQyXpZu oeufZr+4zYxoTgeyzU6P2wBsGDnVF2bF/ckzgOiCrtMyJVkQmlqYK5A6nGw+X05qe5NAjHSXAe88LgxMstQQTyYlVW8UXDf7e4m0oKj6B8t7+9FYlaV9erwU8V+v/WPjdSdH55RqWs7Pq7j5nuNalY0KJb2K4YoHckVFF3ZutQCTPFOEKnCz2YCfrRC3+FXWRlvwYEKcCA3nq552V0vG1Co15Z7uBmKt5nzLV4O174JE5NVeRRzBdvs8ZuxxqOcXCgOeXzX9TAQyGyQsMWzO5/VLNNQ== 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 09:00:06AM -0600, Nico Pache wrote: [...] >@@ -1587,10 +1749,11 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, > if (result == SCAN_SUCCEED) { > /* collapse_huge_page expects the lock to be dropped before calling */ > mmap_read_unlock(mm); >- result = collapse_huge_page(mm, start_addr, referenced, >- unmapped, cc, HPAGE_PMD_ORDER); >- /* collapse_huge_page will return with the mmap_lock released */ >+ nr_collapsed = mthp_collapse(mm, vma, start_addr, referenced, >+ unmapped, cc, enabled_orders); >+ /* mmap_lock was released above, set lock_dropped */ > *lock_dropped = true; >+ result = nr_collapsed ? SCAN_SUCCEED : SCAN_FAIL; Hmm ... don't we lose the allocation-failure result here? Previously collapse_scan_pmd() propagated SCAN_ALLOC_HUGE_PAGE_FAIL from collapse_huge_page(), so khugepaged would call khugepaged_alloc_sleep() in khugepaged_do_scan(). Now if allocation fails and nr_collapsed stays 0, we just return SCAN_FAIL. So we won't back off via khugepaged_alloc_sleep() anymore? Cheers, Lance