From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 315AC3DC4CC; Thu, 10 Sep 2026 11:06:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.113 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789038419; cv=none; b=StvChwrSV2yR+QrNhTDkiw6/NueWNMOdOXePIunUCDa4s1wuGyVdoPnZG/QE0ZeOrt3qBooXzKJWARcQ9qfTddzxDd2c8LqcxXdGSIP0EOMtzoogqzoYaTdgztb3VQbhukB/uiGpc33jN0S5tBpvD/6dbhRUkKEISHayh+ifROo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789038419; c=relaxed/simple; bh=+XjRVKhQvX210fqS/8gQuurVMWMufhoPHiPSRHxpXF0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=is2Heg8Cw+xp/mTTycO7P8ju3eCXll4+FdMl5Y4YUAqHeXHyU52DR3oLLL40JrXnH8qNKjYm91P7p3aoZv6TZR9ovly+2+xfNQr4SbiclLedxmGvVstLtl1WhP4lg4rriOqygcRnpEMLFYmsnXeix00QUAwJ6FBqXctwEooBX70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=XGLdUSDF; arc=none smtp.client-ip=115.124.30.113 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="XGLdUSDF" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1789038413; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=NnCzMKK6Rrt9YRz206NHU/MZ6Oa3TFT+q8PJel2ZDiU=; b=XGLdUSDFdIl9o3rb6kOQi5gFJzhi/kqh982A9jROA+p4VFaYatRIdcDvPai4PISAQM8MDlA85iXGS2YoqvTRjsa7XhyRhJl1ynWcfK4WvqzslommKpc3UnsCuPZyM31bsyDSNAOzBAINxXAfi9MnLGuN4acxjqsjieWOBQ3oRHc= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R901e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=26;SR=0;TI=SMTPD_---0XAhNhUn_1789038410; Received: from 30.74.144.116(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XAhNhUn_1789038410 cluster:ay36) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 19:06:51 +0800 Message-ID: Date: Thu, 10 Sep 2026 19:06:49 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 06/19] selftests/mm: stop khugepaged during the MADV_COLLAPSE cases To: Kiryl Shutsemau Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, rppt@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, usama.anjum@arm.com, usama.arif@linux.dev, nico.pache@linux.dev, ziy@nvidia.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, agordeev@linux.ibm.com, jgg@ziepe.ca, leon@kernel.org, kernel-team@meta.com References: <20260908125105.1510704-1-kirill@shutemov.name> <20260908125105.1510704-7-kirill@shutemov.name> <4e064b9d-aea9-485a-8547-3830999cff01@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/10/26 6:59 PM, Kiryl Shutsemau wrote: > On Thu, Sep 10, 2026 at 02:27:28PM +0800, Baolin Wang wrote: >> >> >> On 9/9/26 6:41 PM, Kiryl Shutsemau wrote: >>> On Wed, Sep 09, 2026 at 05:55:01PM +0800, Baolin Wang wrote: >>>> >>>> >>>> On 9/8/26 8:50 PM, Kiryl Shutsemau wrote: >>>>> From: "Kiryl Shutsemau (Meta)" >>>>> >>>>> __madvise_collapse() turns THP off before each MADV_COLLAPSE, both to keep >>>>> khugepaged out of the range and to prove MADV_COLLAPSE ignores the setting. >>>>> It clears the global controls only, which is no longer enough. A per-order >>>>> control overrides them, and -s, which makes the cases fault in folios of >>>>> one order, leaves that order's control at "always". khugepaged then >>>>> collapses the very range the case is working on, and the case fails on a >>>>> collapse that was interfered with rather than refused. >>>> >>>> Right. So I think the correct fix tag is b7f16963efe7 ("mm/khugepaged: run >>>> khugepaged for all orders"), because before this commit, khugepaged would >>>> not try to collapse this range since it only checked whether the PMD order >>>> was suitable for collapse. >>> >>> Agreed. The series is in mm-new already; if a respin is needed I will use >>> that tag. >>> >>>>> @@ -547,9 +547,16 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages, >>>>> /* >>>>> * Prevent khugepaged interference and tests that MADV_COLLAPSE >>>>> * ignores /sys/kernel/mm/transparent_hugepage/enabled >>>>> + * >>>>> + * "inherit" rather than "never" so that MADV_COLLAPSE on shmem still >>>>> + * finds an order to build. >>>>> */ >>>>> settings.thp_enabled = THP_NEVER; >>>>> settings.shmem_enabled = SHMEM_NEVER; >>>>> + for (i = 0; i < NR_ORDERS; i++) { >>>>> + settings.hugepages[i].enabled = THP_INHERIT; >>>>> + settings.shmem_hugepages[i].enabled = SHMEM_INHERIT; >>>>> + } >>>> >>>> This looks like a workaround to me. Shouldn't we fix this in shmem instead? >>> >>> Good point. >>> >>> It can be a follow-up patch. Do you want to make a proper shmem.c fix >>> and update the selftest along with it? >> >> Either way works for me. > > Please, do it as a standlone shmem fix, plus selftest update to reflect > the change. Ah, sorry, I misunderstood your points. I'll send out a fix patch tomorrow.