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 989B123D281 for ; Thu, 12 Feb 2026 19:51:41 +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=1770925901; cv=none; b=tQrzj3VVqnzkkg2V1ga6+lplT0VjfBdIWcGfMlaZFsX4PtzyrhFIvgRH7nJ8q85vRV6kA1MQZhLUWKcexdQ0Dvlzr18zYvnAKB+6rqolC/r5Xs1ZhM5x0vHTkpcS60MAFjP4jnSl1AdUp6YQsZUUz5C+D7t+tquw7wEU07h7FIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770925901; c=relaxed/simple; bh=ZGlUyowuJ/4IhUY0sQZKkJjYbYXoo0csOOP4hmRvPAg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VJFWnd0Wa6QKWC3D4ERQEVknm1Szt6XDyt9rnqdtM1a6Gzlw3liH8ES1OP0Yaebx3wr0O6s3+D4dDvYBN0eOP82L5jcCz3sphP9W5CpmsOTu3LDfqKfRgevMC7qtRjvUul3EOoo8OCTn8Vp7qeGPLFyP89Pw8YJQx2DnKKKuXfU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Fu2UCV+t; 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="Fu2UCV+t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1138C19424; Thu, 12 Feb 2026 19:51:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770925901; bh=ZGlUyowuJ/4IhUY0sQZKkJjYbYXoo0csOOP4hmRvPAg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Fu2UCV+tTzXaMHiosOBdTGAwWf2IhsIEijmp8dmTq06u07heLkC9cO9U4SLPg+L41 5kDBzKJRACdJrJk4emsWT5IeM6TShLLPOm/Srk3fcqFkxkitXoU1GffsUHFMDhiHZL F/a7DN5FHcza8ctSzBqf+Ji9HhDrbl81F06giV0kJVvZ7S7M+KfrtbJqB4KIUpve4z 5jiGNy+QLZ7Sco/XLsM5Hp2NvrBjLF1BK1c9ZtDui7bTxRg3Mp11to3rJpGs6eB7U5 roiBruCj9Gqo916l8+Py+01JWQqwzafZ2CrHnE/QddfSoHuH+MogfRK0LtDfACY2k6 rAU3BhXv/6j9w== Message-ID: <493d7898-c959-42ee-ad09-35ffc631ec21@kernel.org> Date: Thu, 12 Feb 2026 20:51:26 +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 mm-unstable v1 3/5] mm/khugepaged: define COLLAPSE_MAX_PTES_LIMIT as HPAGE_PMD_NR - 1 To: Nico Pache , linux-kernel@vger.kernel.org, linux-mm@kvack.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, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, 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 References: <20260212021835.17755-1-npache@redhat.com> <20260212021835.17755-4-npache@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/12/26 03:18, Nico Pache wrote: > The value (HPAGE_PMD_NR - 1) is used often in the khugepaged code to > signify the limit of the max_ptes_* values. Add a define for this to > increase code readability and reuse. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index c362b3b2e08a..3dcce6018f20 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -85,6 +85,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); > * > * Note that these are only respected if collapse was initiated by khugepaged. > */ > +#define COLLAPSE_MAX_PTES_LIMIT (HPAGE_PMD_NR - 1) > unsigned int khugepaged_max_ptes_none __read_mostly; > static unsigned int khugepaged_max_ptes_swap __read_mostly; > static unsigned int khugepaged_max_ptes_shared __read_mostly; > @@ -252,7 +253,7 @@ static ssize_t max_ptes_none_store(struct kobject *kobj, > unsigned long max_ptes_none; > > err = kstrtoul(buf, 10, &max_ptes_none); > - if (err || max_ptes_none > HPAGE_PMD_NR - 1) > + if (err || max_ptes_none > COLLAPSE_MAX_PTES_LIMIT) > return -EINVAL; > > khugepaged_max_ptes_none = max_ptes_none; > @@ -277,7 +278,7 @@ static ssize_t max_ptes_swap_store(struct kobject *kobj, > unsigned long max_ptes_swap; > > err = kstrtoul(buf, 10, &max_ptes_swap); > - if (err || max_ptes_swap > HPAGE_PMD_NR - 1) > + if (err || max_ptes_swap > COLLAPSE_MAX_PTES_LIMIT) > return -EINVAL; > > khugepaged_max_ptes_swap = max_ptes_swap; > @@ -303,7 +304,7 @@ static ssize_t max_ptes_shared_store(struct kobject *kobj, > unsigned long max_ptes_shared; > > err = kstrtoul(buf, 10, &max_ptes_shared); > - if (err || max_ptes_shared > HPAGE_PMD_NR - 1) > + if (err || max_ptes_shared > COLLAPSE_MAX_PTES_LIMIT) > return -EINVAL; > > khugepaged_max_ptes_shared = max_ptes_shared; > @@ -384,7 +385,7 @@ int __init khugepaged_init(void) > return -ENOMEM; > > khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; > - khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; > + khugepaged_max_ptes_none = COLLAPSE_MAX_PTES_LIMIT; > khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; > khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2; Changing these is ok. I don't like the name either. It should be clear that they all belong to the "khugepaged_max_ptes" * values. (see below) > > @@ -1869,7 +1870,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > bool is_shmem = shmem_file(file); > > VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); > - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); > + VM_BUG_ON(start & (COLLAPSE_MAX_PTES_LIMIT)); > > result = alloc_charge_folio(&new_folio, mm, cc); > if (result != SCAN_SUCCEED) > @@ -2209,7 +2210,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > * unwritten page. > */ > folio_mark_uptodate(new_folio); > - folio_ref_add(new_folio, HPAGE_PMD_NR - 1); > + folio_ref_add(new_folio, COLLAPSE_MAX_PTES_LIMIT); > > if (is_shmem) > folio_mark_dirty(new_folio); > @@ -2303,7 +2304,7 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned > memset(cc->node_load, 0, sizeof(cc->node_load)); > nodes_clear(cc->alloc_nmask); > rcu_read_lock(); > - xas_for_each(&xas, folio, start + HPAGE_PMD_NR - 1) { > + xas_for_each(&xas, folio, start + COLLAPSE_MAX_PTES_LIMIT) { > if (xas_retry(&xas, folio)) > continue; > Changing these is not. They are semantically something different. E.g., folio_ref_add() adds "HPAGE_PMD_NR - 1" because we already obtained a reference, and we need one per page -- HPAGE_PMD_NR. So it's something different than when messing with the magical khugepaged_max_ptes_none values. -- Cheers, David