From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2E6BB2BE629 for ; Wed, 14 Jan 2026 11:18:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768389512; cv=none; b=Wm8C82I0nQekbM4wylEFPSGx85q7sSc2fkzXuoRWtnhnCWuaaGnjdO532Z9gVtRsRaY+BQ43MkmqDE0LQqxKrT6di5PhFV3kqcFtHy7N34Vur8efXu9x1bTzTwAhLtdyoVROfE9PnMYuG77f1MWI8Se/bBcFb9k0Nvih5m/fxfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768389512; c=relaxed/simple; bh=GXzJ+yUfp9XANjqi1yZT8WBcSpKtfiye6aaL8wZUsR4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Nb1D8s1H6ZIrFqOIz8xPcfVPZbAyXGdT6YaFICDByBFwIx7eM89vqeBJw+Q5h29ETtE0/P7oF86paFOHDf30lrOhggWRtxXiaXbvwrjozhxKjtgiGbTPqWV6Kt5XxvpS+Rr6NuEuzxD5OcepRZVbpufwEO+cMGJ4gcKApFun83U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GM3XGH6q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GM3XGH6q" 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 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 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 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