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Received: from 30.74.144.119(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XAeWyTK_1788947701 cluster:ay36) by smtp.aliyun-inc.com; Wed, 09 Sep 2026 17:55:03 +0800 Message-ID: <4e064b9d-aea9-485a-8547-3830999cff01@linux.alibaba.com> Date: Wed, 9 Sep 2026 17:55:01 +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 , akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, rppt@kernel.org Cc: 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, "Kiryl Shutsemau (Meta)" References: <20260908125105.1510704-1-kirill@shutemov.name> <20260908125105.1510704-7-kirill@shutemov.name> From: Baolin Wang In-Reply-To: <20260908125105.1510704-7-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7C152C000B X-Stat-Signature: cx67pjanmxnhuyrqinru7usnq54wb91x X-Rspam-User: X-HE-Tag: 1788947708-960666 X-HE-Meta: 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 /HiakYrB rAOF/+6Vo2p4OyEU46iJXck0QcfsM5rFCV4VG2lYH+ZlpJi0vGO2fRH4342a6+Kx8ENeW17F9OamsrVEzQf18sEbhCaR2jlnZoB/PBmPuqIx8TVcO4VWfPwMzSOw8lSs7JxbYMCR/b7pQ44e6psc0QoylOJaMcJ0whUp98kW6wgbkKnX5KvtMjszfhHzZOLL7LP0At2fSI0z6k07CbuyjwMO0r6rm4n5lm3n6RvPHLo9E9QzB7mMpCWivUzrfZ1AEphdzwg5B6H0epl8C0jJQEMI+op+fJV6XnlaMuhiIbE97Q4Tm9riOwnLilqxSXBZUPkU5bD9z0hHhS+2N1KrUVDWvn/QEsU5MasKfQnkqmJXEUT4oxdpV5E/8Tlv20zmTphbe Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. > Clear the per-order controls too, setting them to "inherit" rather than > "never": khugepaged honours the global never and stays out, while > MADV_COLLAPSE on shmem still finds an order to build. > > Fixes: 9f0704eae8a4 ("selftests/mm/khugepaged: enlighten for multi-size THP") > Assisted-by: LLM > Signed-off-by: Kiryl Shutsemau (Meta) > --- > tools/testing/selftests/mm/khugepaged.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > index 398430c33872..e9bc8fe8a1f8 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -533,8 +533,8 @@ static bool is_anon(struct mem_ops *ops) > static void __madvise_collapse(const char *msg, char *p, int nr_hpages, > struct mem_ops *ops, bool expect) > { > - int ret; > struct thp_settings settings = *thp_current_settings(); > + int ret, i; > > ksft_print_msg("%s...", msg); > > @@ -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? Since MADV_COLLAPSE is supposed to ignore the THP setting, the fix should be something like this? diff --git a/mm/shmem.c b/mm/shmem.c index c92ed17dbc4a..e0c0901c34a4 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2050,7 +2050,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, global_orders = shmem_huge_global_enabled(inode, index, write_end, shmem_huge_force, vma, vm_flags); /* Tmpfs huge pages allocation */ - if (!vma || !vma_is_anon_shmem(vma)) + if (!vma || !vma_is_anon_shmem(vma) || shmem_huge_force) return global_orders; /*