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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cdce10153sm56391225e9.4.2026.09.01.01.37.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 01:37:36 -0700 (PDT) Date: Tue, 1 Sep 2026 09:37:35 +0100 From: David Laight To: Mike Rapoport Cc: Eli Billauer , 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: <20260901093735.3f5b2df2@pumpkin> In-Reply-To: References: <20260830-char-misc-v1-0-05e2ce44f291@kernel.org> <20260830-char-misc-v1-2-05e2ce44f291@kernel.org> <20260831123937.32255a49@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8C453A0004 X-Stat-Signature: kdz8rzo3nhbp9671d7yfhurgwi5jt5qm X-HE-Tag: 1788251858-865106 X-HE-Meta: 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 7K73I6xN 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 1 Sep 2026 10:59:16 +0300 Mike Rapoport wrote: > On Mon, Aug 31, 2026 at 12:39:37PM +0100, David Laight wrote: > > On Mon, 31 Aug 2026 12:13:08 +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). > > > > Would it really make sense to allocate the four buffers separately? > > And/or use vmalloc(). > > My understanding is that the buffers don't need to be physically > contiguous and vmalloc()ing the entire fifo->mem in one go should work. What is the minimum size? Remember PAGE_SIZE can be 64k. David > > Eli, what do you think? > > > David >