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Thu, 22 Oct 2026 02:05:20 -0700 (PDT) Received: from [192.168.1.18] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a203a4fec8sm57925135e9.13.2026.10.22.02.05.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Oct 2026 02:05:19 -0700 (PDT) Message-ID: Date: Thu, 22 Oct 2026 11:05:18 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: "Jose A. Perez de Azpillaga" Subject: Re: [PATCH v2 5/5] mm: hugetlb: enable CMA allocation for PMD-sized pages To: Qi Zheng , muchun.song@linux.dev, david@kernel.org, osalvador@suse.de, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng , lance.yang@linux.dev References: <5edd1dc82bd3b0b09005c0b36cafa2f7baea6d3d.1792651104.git.zhengqi.arch@bytedance.com> Content-Language: en-US In-Reply-To: <5edd1dc82bd3b0b09005c0b36cafa2f7baea6d3d.1792651104.git.zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/22/26 9:31 AM, Qi Zheng wrote: > From: Qi Zheng > > Allow hugetlb_cma=@ to select the architecture's PMD > size in addition to its existing CMA size. PMD pages are 2M on x86-64 and > 2M, 32M or 512M on arm64 with 4K, 16K or 64K base pages. > > Give PMD pages their own pool while preserving the existing sharing among > gigantic sizes. Unsuffixed arguments and an explicit default size continue > to configure the default pool. Gigantic PMD sizes retain access to that > pool when no PMD pool is reserved. Apply this mapping consistently to > allocation, CMA-only policy and boot-time accounting. > > Try buddy allocation first for non-gigantic PMD pages, with CMA as a > fallback, to reduce CMA migration and leave CMA capacity for later > allocations. Preserve CMA-only policy and CMA-first allocation for > gigantic pages. on v1 you told Lance [1]: > The same missing PF_MEMALLOC_PIN check also affects 1 GiB CMA > allocations, so I had planned to fix it separately. why did v2 go out before the fix then? 1G CMA pins fail with -ENOMEM today, so it's this patch that makes it hang. [1] https://lore.kernel.org/all/04c89538-28c8-4d03-92c1-08d854a46ac4@linux.dev/ -- cheers, jose a. p-a