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b=uTxKO25Q3lp4k/cz11UHz7xs3eo5AZMNGXlVh3BPRLQoDE7vDuj1Mh25s61gOSTw9/NEk3AaTRZylx/vjSbiBwo5lwDBSe5EulAUWAcVJ7e3LJAebE1KFmaSnye7BVb8aGndPVifiLV43c81TQaGeOrMFJvRA5tZzu9GpfHQW18= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam011083073210;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=27;SR=0;TI=SMTPD_---0XAeEI2m_1788940276; Received: from 30.74.144.119(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XAeEI2m_1788940276 cluster:ay36) by smtp.aliyun-inc.com; Wed, 09 Sep 2026 15:51:18 +0800 Message-ID: <238965b3-c512-48f8-8dbb-08a76cdbcc48@linux.alibaba.com> Date: Wed, 9 Sep 2026 15:51:16 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 02/19] selftests/mm: skip collapse_compound_extreme() where the PMD is too large 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> <20260908125105.1510704-3-kirill@shutemov.name> From: Baolin Wang In-Reply-To: <20260908125105.1510704-3-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 96A4A20006 X-Stat-Signature: 9wy5o6rm64kcbaots9mqibugcydswyp9 X-Rspamd-Server: rspam01 X-HE-Tag: 1788940283-564168 X-HE-Meta: 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 y6aJIBpc MVd7KAa4vyCs6VHf2XkL0piBfVV8k/VBMZVhSAeSGX2kle5WwfnQHX0t0VtcsorHJP4KFjrfGr6u8QJvgip+f3rCDpHNnb3Gd8vYQ6K43poc+qBiQDEqWbm+Rl5DnOXhVwBit+Xv3pcpzWF/TUBohz4CdexGUl9D5aLNf/4dSHvj9PYkpHgOp5XBUjLON9rLawxVHY1kI04754KMsCRrDIC4f7V2ftRWVsr5ZlIGR4Tk0etWdGmgcT2shCOZulZ+CmaQw/T1smgrz843LpZbVEBfeZkDDrf2nx3lUnqI8obAgOJaEvHcGqfOYBoLkGcjTTuKQEWlbVvK2NEjTzD45brQBf+uwoNgJ2bySYspYj74lFp7K+kQ1jsBp/0iA16ogtPwXZR9a75s/OapPO8Wx/zUSiz5snTRKfsMWEsyW1NB9tb/jt+X+klzH6g== 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)" > > collapse_compound_extreme() builds a PTE table full of distinct PTE-mapped > compound pages by cycling hpage_pmd_nr fault-time THPs through mremap. It > therefore needs hpage_pmd_nr PMD-order allocations in a row. That is fine > at a 2M PMD (4K base pages) or a 32M one (16K). A 512M PMD -- arm64 with > 64K base pages -- makes each of those an order-13 allocation, which the > allocator cannot reliably hand out even once, let alone 8192 times. > > The failure is not a quiet one: the case calls ksft_exit_fail_msg(), so the > whole binary stops and every case after it is lost. > > Skip the case where the PMD is larger than 32M. The MADV_COLLAPSE cases > still cover PMD-order collapse on those configurations, and 4K and 16K > PMDs are unaffected. > > Assisted-by: LLM > Acked-by: Lorenzo Stoakes (ARM) > Reviewed-by: Mike Rapoport (Microsoft) > Tested-by: Muhammad Usama Anjum > Signed-off-by: Kiryl Shutsemau (Meta) > --- LGTM. Reviewed-by: Baolin Wang