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 9D4331F37BE for ; Tue, 17 Dec 2024 17:09:48 +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=1734455391; cv=none; b=rHT/qHzzC8Wg8x0BYKcZ4oOGgeYI7G5XVQBhrquVSGQ9lf73PzJ0NjyyVaXEc492hHOlj14Zb6xqZRakXabemoerxh9C5SqI7QUs3sAFDO8jFHOZBUtQ19FuXw4KT9eiLswiJP8YBYjzQr/jfTRbCWd1ljylSGfF0DvudqmA+rc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734455391; c=relaxed/simple; bh=uGZYXrfVPJL0VviBMmCM3Pll7/4KrxvbhxdKOvJn/+M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MM6iREkEJJdwZXx+u3SoXD/qzm54pXAwwhtC2K966YFqrBfzpsbYsSsftsdPy2Co39ceOfBs/i3pJGj0rhGRIUNZxoYxpBaNizSL358UezPZIJJw+YzgOBicrkRUcUo2TIWJKk5ZGRJjk+IeQpiD/ZN6ki/2ggRGFQFPInf8qYM= 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 B7B6DFEC; Tue, 17 Dec 2024 09:10:15 -0800 (PST) Received: from [10.57.91.184] (unknown [10.57.91.184]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1DE703F7B4; Tue, 17 Dec 2024 09:09:41 -0800 (PST) Message-ID: <23e93e90-0681-4039-a3bb-f4b01b8eefeb@arm.com> Date: Tue, 17 Dec 2024 17:09:40 +0000 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 05/12] khugepaged: Generalize __collapse_huge_page_isolate() Content-Language: en-GB To: Dev Jain , 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> <20241216165105.56185-6-dev.jain@arm.com> From: Ryan Roberts In-Reply-To: <20241216165105.56185-6-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/12/2024 16:50, Dev Jain wrote: > Scale down the scan range and the sysfs tunables according to the scan order, > and isolate the folios. > > Signed-off-by: Dev Jain > --- > mm/khugepaged.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index f52dae7d5179..de044b1f83d4 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -564,15 +564,18 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > unsigned long address, > pte_t *pte, > struct collapse_control *cc, > - struct list_head *compound_pagelist) > + struct list_head *compound_pagelist, int order) > { > - struct page *page = NULL; > - struct folio *folio = NULL; > - pte_t *_pte; > + unsigned int max_ptes_shared = khugepaged_max_ptes_shared >> (HPAGE_PMD_ORDER - order); > + unsigned int max_ptes_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - order); This is implicitly rounding down. I think that's the right thing to do; it's better to be conservative. > int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; > + struct folio *folio = NULL; > + struct page *page = NULL; > bool writable = false; > + pte_t *_pte; > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; > + > + for (_pte = pte; _pte < pte + (1UL << order); > _pte++, address += PAGE_SIZE) { > pte_t pteval = ptep_get(_pte); > if (pte_none(pteval) || (pte_present(pteval) && > @@ -580,7 +583,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > ++none_or_zero; > if (!userfaultfd_armed(vma) && > (!cc->is_khugepaged || > - none_or_zero <= khugepaged_max_ptes_none)) { > + none_or_zero <= max_ptes_none)) { > continue; > } else { > result = SCAN_EXCEED_NONE_PTE; > @@ -609,7 +612,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > if (folio_likely_mapped_shared(folio)) { > ++shared; > if (cc->is_khugepaged && > - shared > khugepaged_max_ptes_shared) { > + shared > max_ptes_shared) { > result = SCAN_EXCEED_SHARED_PTE; > count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); > goto out; > @@ -1200,7 +1203,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl); > if (pte) { > result = __collapse_huge_page_isolate(vma, address, pte, cc, > - &compound_pagelist); > + &compound_pagelist, order); > spin_unlock(pte_ptl); > } else { > result = SCAN_PMD_NULL;