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Received: from 30.74.144.116(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XAgmcIa_1789021649 cluster:ay36) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 14:27:30 +0800 Message-ID: Date: Thu, 10 Sep 2026 14:27:28 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 06/19] selftests/mm: stop khugepaged during the MADV_COLLAPSE cases To: Kiryl Shutsemau Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, rppt@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, usama.anjum@arm.com, usama.arif@linux.dev, nico.pache@linux.dev, ziy@nvidia.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, agordeev@linux.ibm.com, jgg@ziepe.ca, leon@kernel.org, kernel-team@meta.com References: <20260908125105.1510704-1-kirill@shutemov.name> <20260908125105.1510704-7-kirill@shutemov.name> <4e064b9d-aea9-485a-8547-3830999cff01@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 01EAD40003 X-Stat-Signature: o4truh6icma3trqubebmpy4ccx4of44j X-Rspam-User: X-HE-Tag: 1789021656-769527 X-HE-Meta: U2FsdGVkX1+zjg0TITVQ4zZrGdwpaSjiXogji3w5TrISp2Yqg0QOyEyymjOyRj+fh/DIRP0Kc+5P6KXFPE12mlgD/lTOEAgDI/LRSJMcjfC0D8Ro16K1sAzNPLxZB5E9XvbzEytT4LOsTHPwCsGzMjRiU4ThBujELeOKYoLWV7P1ai7D8YUqbp6qXbe0+eAy6q/DiNewHEz8jtSxaSANc6Jmoa30Le3UHLF/SYyDafOorQwM8IP0BBpZNIJYZJ54sNG34A3Wr55k3YdJZllBeWEKgBf7rLUEA6TKBqJup50JIeHS4cwW2wAKfXk4JgeW+gOhdo1HBIuULbnTclfSKLdtP2f8lLBr6iFiBF2waGj+/MpMNSWU9sXndH2jA2APqSlK6NvqM4cCSde3xQov8Bu2j8LAwQjkFAwkvLkmyNP0HCH+rtim7ob7119mOyQML1AzLAWwB7MhJiwWVZay1IzZj4DnjH43SycEh8lKV6Pz0/CS63w62qW7NM196bE4vF6R0VhlXv6sIqRzFR7m7OkQoj0Dgpp9isjCYHT5gmH+wJKvxrxejwj85QLJdgH2nnhfm5uWk7KHFaRCbfXU85zSO2ULBgqWZMgRUhwz+2l1wiIbL0T56qtm4DVGCNAr4Jw4VuKBPezijL8snz8CpSobVxVPSgF3BLQpyyxuBgYNAAkJ0Mve8unu3tNNESYCxTI5ErUbqKl+Oe51YHQR8MyNJNMSdeAN1/qDyu5kj+D4ajLFQWOX0ibcJQpHcnl/0x8OgxrMcRWZOC8CimxHsD2fwgYsYJm7sqgc1OZ0yKgQmI+lwD9hD1YhAM6Qmcn4oyTYPQbzOeTO/tv3//jx508MN/XS5NYmIf9nwfqB88TxwEr5mygIIGZLnb4pSS2Hed5DemPscWIGjo9l0a9ji1Ko/hSpGLsG5TFs3q+XcxMjeEIBlIFI03MQFLC8YufSSMFE49VeFescM/MHaWH IG7Xt4x4 DwBk3X+/6CTxIKSyPkpIB17DW7OCqY8ReaQ+xfxt/K9vgbzuiYAZKOwy1/7tLHnhH9MOUPWKXtEMPX7UW5ERjqzU6EwTYSVT2pFnkEW7a3ImF1KdlwcO7O85kUeRTzcxYQhGazFhr7Z+Y5wZRMQo1P7hXkCkDHAao4a8FhOEhHxLZ5XyRXMUzELE9TqsrKJfx+axj/E5caT7b6uRxCMN1dsxspR59feDc/Es+jc74K9Lmbca5Iwj7pss3G7Rtz/GRl7/0ci3tcfJoAcSRcqwlMaVJh9IsntZfT3878BsEhU817v6Mwg3mpeoAv34lovvQ0j0Rf4p4ng3SJH9OnUrxJXJHZImhlibAGsu76DxOHL/l3Q+pFKAyRZgMLIJ0ZW0bvjY5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/9/26 6:41 PM, Kiryl Shutsemau wrote: > On Wed, Sep 09, 2026 at 05:55:01PM +0800, Baolin Wang wrote: >> >> >> On 9/8/26 8:50 PM, Kiryl Shutsemau wrote: >>> From: "Kiryl Shutsemau (Meta)" >>> >>> __madvise_collapse() turns THP off before each MADV_COLLAPSE, both to keep >>> khugepaged out of the range and to prove MADV_COLLAPSE ignores the setting. >>> It clears the global controls only, which is no longer enough. A per-order >>> control overrides them, and -s, which makes the cases fault in folios of >>> one order, leaves that order's control at "always". khugepaged then >>> collapses the very range the case is working on, and the case fails on a >>> collapse that was interfered with rather than refused. >> >> Right. So I think the correct fix tag is b7f16963efe7 ("mm/khugepaged: run >> khugepaged for all orders"), because before this commit, khugepaged would >> not try to collapse this range since it only checked whether the PMD order >> was suitable for collapse. > > Agreed. The series is in mm-new already; if a respin is needed I will use > that tag. > >>> @@ -547,9 +547,16 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages, >>> /* >>> * Prevent khugepaged interference and tests that MADV_COLLAPSE >>> * ignores /sys/kernel/mm/transparent_hugepage/enabled >>> + * >>> + * "inherit" rather than "never" so that MADV_COLLAPSE on shmem still >>> + * finds an order to build. >>> */ >>> settings.thp_enabled = THP_NEVER; >>> settings.shmem_enabled = SHMEM_NEVER; >>> + for (i = 0; i < NR_ORDERS; i++) { >>> + settings.hugepages[i].enabled = THP_INHERIT; >>> + settings.shmem_hugepages[i].enabled = SHMEM_INHERIT; >>> + } >> >> This looks like a workaround to me. Shouldn't we fix this in shmem instead? > > Good point. > > It can be a follow-up patch. Do you want to make a proper shmem.c fix > and update the selftest along with it? Either way works for me.