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imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GM3XGH6q; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768389512; a=rsa-sha256; cv=none; b=D3Mn8XivYLHmldPpi0/UcLVO63pFtzt7XJjHKeBxzknzARDL4ojBXxnkY25F8vwqxtjHzQ 2nyErTCA0+9OEZQcKZpBaYlM7J10yamc9dwjrIYLDPYoClYGt/Dba9p2fugt8ta1m4SkJ3 unIRaOw0sELDYPm4WhMrAdhoROEjUCU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1FEC16001D; Wed, 14 Jan 2026 11:18:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36431C4CEF7; Wed, 14 Jan 2026 11:18:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768389511; bh=GXzJ+yUfp9XANjqi1yZT8WBcSpKtfiye6aaL8wZUsR4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=GM3XGH6qaq0giaJbLi7IiZASEJJdj4aadn89uMm1v1Gb2HffgqLrfYU2Tewjn1DC9 qpHfCGeVi2bSqU1N2994EKZdplfN7vdg0dM5SwxJNjeDXRJipkBJpFqlU80bfUsg/y 5RQhhIdT/l2+8BjJdjv0jMbGNt6SG85w+wyEtv+WLjoh6qJdjt/3IQiz6WZq03WLgZ BWb9w4azxFML4P+NeOiPr1US0/8zZwpkqt1ay7+WWMZW4xAfENWwnIP3yR0lw0k63Q 9DfKg0ouGb2kmfhQypNFbx2KSA89+8O47L5exU9SE8W9AaMxXwTFw7Cf4iqsj5hQx8 ZBbJF5MFDIGsg== Message-ID: <512dab18-483a-4cf0-976b-d37806d3da35@kernel.org> Date: Wed, 14 Jan 2026 12:18:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/6] mm: khugepaged: refine scan progress number To: Vernon Yang Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, richard.weiyang@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang References: <20260104054112.4541-1-yanglincheng@kylinos.cn> <20260104054112.4541-3-yanglincheng@kylinos.cn> <69c9ac59-4fb2-42fc-a8ae-32f583e47de4@kernel.org> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: mdr951hcwuuog4h9wp6owchwfgfutcnf X-Rspamd-Queue-Id: AA315100012 X-Rspamd-Server: rspam04 X-HE-Tag: 1768389512-563885 X-HE-Meta: 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 To1yFWTr nFZdePDB+oRMTcB8gtT2Tj/nhefYLV1aFIxPjGrWilDt8F8fv/sUIvYIRDvRxx+Em1Np/IhHGpOHGxFr05EnhgTOaeJdamiTu0bQhxg1I8RAwVvBt5h8ymdC02Zbhz8/lKaAp+3e6C6Vdt/Sw/98By2iI4zYkS1zySZg3adCO4gh+imm4c1oS+n111csx8ji5z4pm6qmFcrYmBvTmun5J6fDpxG/7OgrW6yp+hNduE4NucYXdihONEtQR8Wwe5vtBV2GMuzPRwjr+5Pp8W10VQLjsTWAMXm1Hvosv9Ob/FE+tIwoZAydIX5KvAdBXXEMNgKo2LDs3ikde6Hn/98w/4Njv5qn5+VTLEcvTNr7euohPY7oKwP62X37jtPtui2WjvWn90BW9ml7CXVjQiQb4J1G1+51kZK4P0kx+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/6/26 06:55, Vernon Yang wrote: > On Mon, Jan 05, 2026 at 05:49:22PM +0100, David Hildenbrand (Red Hat) wrote: >> On 1/4/26 06:41, Vernon Yang wrote: >>> Currently, each PMD scan always increases `progress` by HPAGE_PMD_NR, >>> even if only scanning a single page. By counting the actual number of >> >> "... a single pmd" ? >> >>> pages scanned, the `progress` is tracked accurately. >> >> "page table entries / pages scanned" ? > > The single page is pte-4KB only. This patch does not change the original > semantics of "progress", it simply uses the exact number of PTEs counted > to replace HPAGE_PMD_NR. You used the right terminology: "PTEs" counted. It could be either a page or a PTE, depending on whether we collapse an anon THP or an file thp. You make it sound like we always scan pages. [...] > >>> >>> Signed-off-by: Vernon Yang >>> --- >>> mm/khugepaged.c | 31 +++++++++++++++++++++++-------- >>> 1 file changed, 23 insertions(+), 8 deletions(-) >>> >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index 9f99f61689f8..4b124e854e2e 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -1247,7 +1247,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, >>> static int hpage_collapse_scan_pmd(struct mm_struct *mm, >>> struct vm_area_struct *vma, >>> unsigned long start_addr, bool *mmap_locked, >>> - struct collapse_control *cc) >>> + int *progress, struct collapse_control *cc) >>> { >>> pmd_t *pmd; >>> pte_t *pte, *_pte; >>> @@ -1258,23 +1258,28 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, >>> unsigned long addr; >>> spinlock_t *ptl; >>> int node = NUMA_NO_NODE, unmapped = 0; >>> + int _progress = 0; >> >> "cur_progress" ? > > Yes. > >>> VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK); >>> result = find_pmd_or_thp_or_none(mm, start_addr, &pmd); >>> - if (result != SCAN_SUCCEED) >>> + if (result != SCAN_SUCCEED) { >>> + _progress = HPAGE_PMD_NR; >>> goto out; >>> + } >>> memset(cc->node_load, 0, sizeof(cc->node_load)); >>> nodes_clear(cc->alloc_nmask); >>> pte = pte_offset_map_lock(mm, pmd, start_addr, &ptl); >>> if (!pte) { >>> + _progress = HPAGE_PMD_NR; >>> result = SCAN_NO_PTE_TABLE; >>> goto out; >>> } >>> for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR; >>> _pte++, addr += PAGE_SIZE) { >>> + _progress++; >>> pte_t pteval = ptep_get(_pte); >>> if (pte_none_or_zero(pteval)) { >>> ++none_or_zero; >>> @@ -1410,6 +1415,9 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, >>> *mmap_locked = false; >>> } >>> out: >>> + if (progress) >>> + *progress += _progress; >>> + >>> trace_mm_khugepaged_scan_pmd(mm, folio, referenced, >>> none_or_zero, result, unmapped); >>> return result; >>> @@ -2287,7 +2295,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, >>> static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, >>> struct file *file, pgoff_t start, >>> - struct collapse_control *cc) >>> + int *progress, struct collapse_control *cc) >>> { >>> struct folio *folio = NULL; >>> struct address_space *mapping = file->f_mapping; >>> @@ -2295,6 +2303,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, >>> int present, swap; >>> int node = NUMA_NO_NODE; >>> int result = SCAN_SUCCEED; >>> + int _progress = 0; >> >> Same here. >> >> >> Not sure if it would be cleaner to just let the parent increment its counter >> and returning instead the "cur_progress" from the function. > > Both are good for me, I have implemented one version as follows, please > see if it is cleaner. From a quick glimpse looks good. -- Cheers David