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 57A1D40B6F6; Tue, 12 May 2026 07:30:06 +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=1778571006; cv=none; b=UefgqOgdL7Fh/hmOnSruCIdpdkHU8r0OKAPdAYBh2wOvWzPLlVDo9yxKRa1l3ZkoK5xPxGon82MSPLj7Z01+/iQaqehgavSspHkdB2DCiEznj2PrRU9DtGXoHu+q/BP10dBiywo+gZINldDnSw+9cT73Vrzf9p1pSobqqp0fqXg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778571006; c=relaxed/simple; bh=jT3UFNwnko997LiCICyDWawsTW8JiqcQq8u0ORL/NYw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qbpGRf2nwTMVUaf1/ZXp1Y2eUo0hZwH44LXHtpkw37ZDvGzj8kMvP6ah3tuTNiy4vJtx/WSgF7jwFTYXQEaBbYjTZKXy+7/C7nt6mXm9oBKE3FasgKvJjvOGzt0g6tyHzhTQE6y58RUIJE93D3yaVD0PHLKabX5HzRjtN+7o1fM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IwXYtNzv; 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="IwXYtNzv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70C1CC2BCB8; Tue, 12 May 2026 07:29:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778571005; bh=jT3UFNwnko997LiCICyDWawsTW8JiqcQq8u0ORL/NYw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=IwXYtNzvpHXt942+2ou0EzI8WRfn+qpcV60EsXotQywCfTd05HTXefMKHQRQYI6yC 84IkUw0axbfJnrdD7w1mOEc/5T4Ls/wRlpOGGWIlo0jAnWLXRND1fg0ZmkjrvKgH7m YNnL1caBBHsMwSzhMYe4+1QGyVjw672IUfmVVkSrCwWKrfYSOJxE5MdpxSIae5Vu6q lMfrmlOmaeFoym7lkbgxsq622WOp028XJii6goIGHlIrKAqERRJsupgASIrYiq3jhJ 2ecDHjN/qodgU49oegYDhBRVwJEmxNzXYSuTWbgG6VEUnlB7nZpc2AGVcWUFoP5tH+ 2ixYzPQ8UrgAg== Message-ID: <4566170a-7e3d-49e4-baab-ba2790c198db@kernel.org> Date: Tue, 12 May 2026 09:29:52 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v17 03/14] mm/khugepaged: rework max_ptes_* handling with helper functions To: Nico Pache , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com, Usama Arif References: <20260511185817.686831-1-npache@redhat.com> <20260511185817.686831-4-npache@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/11/26 20:58, Nico Pache wrote: > The following cleanup reworks all the max_ptes_* handling into helper > functions. This increases the code readability and will later be used to > implement the mTHP handling of these variables. > > With these changes we abstract all the madvise_collapse() special casing > (dont respect the sysctls) away from the functions that utilize them. And > will be used later in this series to cleanly restrict the mTHP collapse > behavior. > > No functional change is intended; however, we are now only reading the > sysfs variables once per scan, whereas before these variables were being > read on each loop iteration. > > Suggested-by: David Hildenbrand > Acked-by: David Hildenbrand (Arm) Some nits when re-reading: > Acked-by: Usama Arif > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 118 +++++++++++++++++++++++++++++++++--------------- > 1 file changed, 82 insertions(+), 36 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index f0e29d5c7b1f..f68853b3caa7 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -348,6 +348,62 @@ static bool pte_none_or_zero(pte_t pte) > return pte_present(pte) && is_zero_pfn(pte_pfn(pte)); > } > > +/** > + * collapse_max_ptes_none - Calculate maximum allowed none-page or zero-page I know, it's painful, but ... There is no "none-page". Calculate maximum allowed empty PTEs or PTEs mapping the shared zeropage ... ? > + * PTEs for the given collapse operation. We usually indent here (second line of subject), I think. Same applies to the other doc below. > + * @cc: The collapse control struct > + * @vma: The vma to check for userfaultfd > + * > + * Return: Maximum number of none-page or zero-page PTEs allowed for the > + * collapse operation. Same here. > + */ > +static unsigned int collapse_max_ptes_none(struct collapse_control *cc, > + struct vm_area_struct *vma) > +{ > + // If the vma is userfaultfd-armed, allow no none-page or zero-page PTEs. Lance commented on the comment style. Is this comment really required? It's pretty self-documenting already. > + if (vma && userfaultfd_armed(vma)) > + return 0; > + // for MADV_COLLAPSE, allow any none-page or zero-page PTEs. > + if (!cc->is_khugepaged) > + return HPAGE_PMD_NR; > + // For all other cases repect the user defined maximum. > + return khugepaged_max_ptes_none; > +} > + -- Cheers, David