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b=AZJyrgmM8QADM/tQ3djTAeARnE0tu71LsYAnpmqOKEj9/Wtt3nwHniVayVY8E0Toa yOc5jOJtEmC3bTWpfpt3zQGdo1fQ9ZleHcWHBaMU8ssVlG+Ke0eEyvGXlXmRFCnQaj 24DWfOWiKUIVTcMRoDf8GLwWworUIMllAjQPrMak3Uhn+2l8psqWw7Z70Ac7fmF9Mj s5xWmHPx0ttQkWplwpmg38jECJ3umgKKp4Q9iMYLezRSHDeetagS7TrEN9nDaw0PxY MWZfkVXytlJKkgMMAQ1j+jROPE42uPqSohV8GVbsUZvr6h+q88wozzSnTj8/xy/yXH LgAp5GZKJQY0w== Date: Mon, 31 Aug 2026 14:32:49 +0300 From: Mike Rapoport To: Eli Billauer Cc: Arnd Bergmann , Brad Warrum , Greg Kroah-Hartman , Michal Simek , Ritu Agarwal , Andrew Morton , David Hildenbrand , Matthew Wilcox , Vlastimil Babka , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 2/4] char: xillybus: replace __get_free_pages() with kmalloc() Message-ID: References: <20260830-char-misc-v1-0-05e2ce44f291@kernel.org> <20260830-char-misc-v1-2-05e2ce44f291@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 4nt6o9qi53cnhat49wg186ys3sbi9eyx X-Rspamd-Queue-Id: A4C2B12000A X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788175978-234447 X-HE-Meta: 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 7nKfROci kizbZRbDv5EIXHUES4TjL2inYsk6nHaVg9I+1trrevhDXzoKlpMZPvonH3qDooWuodujepEYEsWbidChOuPGOEPFiSJuJnXVnIPlTcBNdXH+LAp+J4tDiy0eH5aqvsYJNqiVKHubpKzp+83uqfKRjd85M+5Yj2TYrrqTr7vk2SPQqPgDzrKP/tHrDR1LGA7o4j23ICT6i3KxWe32FC1R+vVIhM7SYDwGuj/OQz6gFIyw2IrbHrjwXdCBRckBEUWg5edT9Ozzqme8TL2x5GMXdFYY6zqUphNpj5s7hc+quJU2bbATBqF6jWLEJ8AvtuoPrrHRaJ0QtwWpGkoJXez30e1wdrL5zmOrtP/XQBXbkBmUGR/JLGxtSSWJqfsUK9J/sAbq+ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 31, 2026 at 12:13:08PM +0200, Eli Billauer wrote: > On 30/08/2026 9:47, Mike Rapoport (Microsoft) wrote: > > fifo_init() allocates the buffers backing the software FIFO and > > endpoint_alloc() allocates the transfer buffers of a USB endpoint. > > > > These buffers can be allocated with kmalloc() as there's nothing special > > about them to go directly to the page allocator. > > Except that they are a bit large. > > fifo_init() may be requested to allocate up to 256 MB of buffer memory. This > memory resource is split into an array of buffers (fifo->mem[i]), each 64 > kiB (or less, if there's trouble obtaining segments of this size). > > Citing Documentation/core-api/memory-allocation.rst: > > "The maximal size of a chunk that can be allocated with `kmalloc` is > limited. The actual limit depends on the hardware and the kernel > configuration, but it is a good practice to use `kmalloc` for objects > smaller than page size." For large sizes kmalloc falls back to page allocator anyway. And the doc is out of date unfortunately. > Regards, > Eli -- Sincerely yours, Mike.