From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id F0A42146590 for ; Wed, 18 Dec 2024 08:49:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734511793; cv=none; b=QbEhFClEyC/ObpHzn77mqDsd7Egv0sm1Cseu2QnUBSTto0v4HCsPjih4zwoe9fwX4ehrrww0kJPUJKdJJ8UeQYtUtFx/QWXqkVy5WLUdqT/sGRxaQKrYRVKPTwaXD0mIJx3MP98vAU+aAOMErMPqcaj60BX43WL/k/6sUFDUsoY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734511793; c=relaxed/simple; bh=pdfXoyfqMvPQPiiOQvGDvdbQU0cqsy8jqKwDlWgH87o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=apfPDbH1OMhxHTYKQNBzWi88c17AsYH1IJ74ZeL1kqSZyELt/86eMJplogNjMqNVf7kDJ9QnrELiEZlw0qxYDZEQsYmUUJ1LCifxHDZrtQKqiXC4UK7If4u9qqZXjstUq14pnofIM2IHxD7zpnLIrNMvVHcEgdUpk6tcoD4DC6g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2F8B41063; Wed, 18 Dec 2024 00:50:19 -0800 (PST) Received: from [10.162.42.42] (K4MQJ0H1H2.blr.arm.com [10.162.42.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D09953F7B4; Wed, 18 Dec 2024 00:49:40 -0800 (PST) Message-ID: <1311738e-c9cc-4667-a758-f20d770ea329@arm.com> Date: Wed, 18 Dec 2024 14:19:37 +0530 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: [RFC PATCH 06/12] khugepaged: Generalize __collapse_huge_page_copy_failed() To: Ryan Roberts , akpm@linux-foundation.org, david@redhat.com, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu, haowenchao22@gmail.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, jglisse@google.com, surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com, zhengqi.arch@bytedance.com, jhubbard@nvidia.com, 21cnbao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241216165105.56185-1-dev.jain@arm.com> <20241216165105.56185-7-dev.jain@arm.com> <4a2554ad-c204-4350-8898-545c1da124bb@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: <4a2554ad-c204-4350-8898-545c1da124bb@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17/12/24 10:52 pm, Ryan Roberts wrote: > On 16/12/2024 16:50, Dev Jain wrote: >> Upon failure, we repopulate the PMD in case of PMD-THP collapse. Hence, make >> this logic specific for PMD case. >> >> Signed-off-by: Dev Jain >> --- >> mm/khugepaged.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index de044b1f83d4..886c76816963 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -766,7 +766,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, >> pmd_t *pmd, >> pmd_t orig_pmd, >> struct vm_area_struct *vma, >> - struct list_head *compound_pagelist) >> + struct list_head *compound_pagelist, int order) > nit: suggest putting order on its own line. > >> { >> spinlock_t *pmd_ptl; >> >> @@ -776,14 +776,16 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, >> * pages. Since pages are still isolated and locked here, >> * acquiring anon_vma_lock_write is unnecessary. >> */ >> - pmd_ptl = pmd_lock(vma->vm_mm, pmd); >> - pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); >> - spin_unlock(pmd_ptl); >> + if (order == HPAGE_PMD_ORDER) { >> + pmd_ptl = pmd_lock(vma->vm_mm, pmd); >> + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); >> + spin_unlock(pmd_ptl); >> + } >> /* >> * Release both raw and compound pages isolated >> * in __collapse_huge_page_isolate. >> */ >> - release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist); >> + release_pte_pages(pte, pte + (1UL << order), compound_pagelist); >> } > Given this function is clearly so geared towards re-establishing the pmd, given > that it takes the *pmd and orig_pmd as params, and given that in the > non-pmd-order case, we only call through to release_pte_pages(), I wonder if > it's better to make the decision at a higher level and either call this function > or release_pte_pages() directly? No strong opinion, just looks a bit weird at > the moment. Makes sense, we can probably get rid of this function and let the caller call reestablish_pmd() or something for the PMD case. > >> >> /* >> @@ -834,7 +836,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio, >> compound_pagelist); >> else >> __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma, >> - compound_pagelist); >> + compound_pagelist, order); >> >> return result; >> }