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Tue, 09 Sep 2025 14:23:32 +0800 Message-ID: <09420e06-5acb-470a-9eb1-5f35d8b2a6bd@linux.alibaba.com> Date: Tue, 9 Sep 2025 14:23:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] mm: skip mlocked THPs that are underused early in deferred_split_scan() To: Lance Yang , akpm@linux-foundation.org, david@redhat.com Cc: Liam.Howlett@oracle.com, baohua@kernel.org, dev.jain@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, npache@redhat.com, ryan.roberts@arm.com, usamaarif642@gmail.com, ziy@nvidia.com References: <20250908090741.61519-1-lance.yang@linux.dev> From: Baolin Wang In-Reply-To: <20250908090741.61519-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B7F0BC000C X-Stat-Signature: 9jjh3xentjuxei9naexjqyxfa3zu15zw X-HE-Tag: 1757399016-939370 X-HE-Meta: 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 7cv2FVaX 8asf0TTz6umZLN00nO8qwPqyFot0odOHNzWczo1E5Ko/P6px+TaW8PrwukYe/Mp5PysjYy/1QR0wQyQpjC9/Jd1NAFZWuP93T1Kye9mW7VYPsQjHzz8zP3N1R9QVt9RrXE86pKqHbNOGH+0GFQzlCdQy7bt9nvZBhxUc0EsYN1iAZDh6m38SrR4qa9gJ16uhO3HKLBtI1vwI9Y+WnWWOVZ2aNq484+71E8hs+zgA19NIa+NRu9v4L9HxCq07euR72auxWNTg9WP0Zf42j5SRZ9fYLWOXBq7EF2AYHd4G7hG1uaCdJiQY0bL2A5EaAYv3dcCsgj5o/OeoPMRrQ1ZKP+KI/871bNghwZOkNXZAGlkFPu8cBsLoYrgbh9YZz2shxXg+s22aVp76loX4= 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 2025/9/8 17:07, Lance Yang wrote: > From: Lance Yang > > When we stumble over a fully-mapped mlocked THP in the deferred shrinker, > it does not make sense to try to detect whether it is underused, because > try_to_map_unused_to_zeropage(), called while splitting the folio, will not > actually replace any zeroed pages by the shared zeropage. > > Splitting the folio in that case does not make any sense, so let's not even > scan to check if the folio is underused. > > Suggested-by: David Hildenbrand > Signed-off-by: Lance Yang > --- LGTM. Reviewed-by: Baolin Wang > v1 -> v2: > - Update subject and changelog (per David, thanks!) > - https://lore.kernel.org/linux-mm/20250908040713.42960-1-lance.yang@linux.dev > > mm/huge_memory.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 77f0c3417973..6d99893c18e8 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -4183,6 +4183,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, > bool underused = false; > > if (!folio_test_partially_mapped(folio)) { > + /* > + * See try_to_map_unused_to_zeropage(): we cannot > + * optimize zero-filled pages after splitting an > + * mlocked folio. > + */ > + if (folio_test_mlocked(folio)) > + goto next; > underused = thp_underused(folio); > if (!underused) > goto next;