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b=JtuEeNyhuCc/L2+UyGaZrIyAVjP+fochYvVo9jPpyjVGvav4q1UJExsrb/C74WXWSUVjNzZiKGyedarvHIPH076iviXZ4RyRJNsS//M48ihMh+EFOUgdonFgu8YPaUQs1klt6GoRy71kUKwSKH4uJyqajrTbkQCb2xKCgP4t4oY= Received: from 30.74.144.114(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WbNVW2L_1747735757 cluster:ay36) by smtp.aliyun-inc.com; Tue, 20 May 2025 18:09:18 +0800 Message-ID: Date: Tue, 20 May 2025 18:09:16 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 06/12] khugepaged: introduce khugepaged_scan_bitmap for mTHP support To: Nico Pache Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, david@redhat.com, ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org References: <20250515032226.128900-1-npache@redhat.com> <20250515032226.128900-7-npache@redhat.com> <9c54397f-3cbf-4fa2-bf69-ba89613d355f@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DD57B18000F X-Stat-Signature: spa6dczwgk9h19gzq6uge54jznn9imsb X-Rspam-User: X-HE-Tag: 1747735763-146627 X-HE-Meta: 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 j/7Ug0Du 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 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: Sorry for late reply. On 2025/5/17 14:47, Nico Pache wrote: > On Thu, May 15, 2025 at 9:20 PM Baolin Wang > wrote: >> >> >> >> On 2025/5/15 11:22, Nico Pache wrote: >>> khugepaged scans anons PMD ranges for potential collapse to a hugepage. >>> To add mTHP support we use this scan to instead record chunks of utilized >>> sections of the PMD. >>> >>> khugepaged_scan_bitmap uses a stack struct to recursively scan a bitmap >>> that represents chunks of utilized regions. We can then determine what >>> mTHP size fits best and in the following patch, we set this bitmap while >>> scanning the anon PMD. A minimum collapse order of 2 is used as this is >>> the lowest order supported by anon memory. >>> >>> max_ptes_none is used as a scale to determine how "full" an order must >>> be before being considered for collapse. >>> >>> When attempting to collapse an order that has its order set to "always" >>> lets always collapse to that order in a greedy manner without >>> considering the number of bits set. >>> >>> Signed-off-by: Nico Pache >> >> Sigh. You still haven't addressed or explained the issues I previously >> raised [1], so I don't know how to review this patch again... > Can you still reproduce this issue? Yes, I can still reproduce this issue with today's (5/20) mm-new branch. I've disabled PMD-sized THP in my system: [root]# cat /sys/kernel/mm/transparent_hugepage/enabled always madvise [never] [root]# cat /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled always inherit madvise [never] And I tried calling madvise() with MADV_COLLAPSE for anonymous memory, and I can still see it collapsing to a PMD-sized THP. > I can no longer reproduce this issue, that's why I posted... although > I should have followed up, and looked into what the original issue > was. Nothing really sticks out so perhaps something in mm-new was > broken and pulled out... not sure. > > It should now follow the expected behavior, which is that no mTHP > collapse occurs because if the PMD size is disabled so is khugepaged > collapse. > > Lmk if you are still experiencing this issue please. > > Cheers, > -- Nico >> >> [1] >> https://lore.kernel.org/all/83a66442-b7c7-42e7-af4e-fd211d8ed6f8@linux.alibaba.com/ >>