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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4843310ab29sm14535272f8f.0.2026.08.31.04.39.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2026 04:39:38 -0700 (PDT) Date: Mon, 31 Aug 2026 12:39:37 +0100 From: David Laight To: Eli Billauer Cc: "Mike Rapoport (Microsoft)" , 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: <20260831123937.32255a49@pumpkin> In-Reply-To: References: <20260830-char-misc-v1-0-05e2ce44f291@kernel.org> <20260830-char-misc-v1-2-05e2ce44f291@kernel.org> 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-Stat-Signature: rkf6yyao45tnm4499oknsbzzcrofwhhf X-Rspamd-Queue-Id: 359DAC0004 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788176380-498034 X-HE-Meta: U2FsdGVkX19MNuFcZG8dMAFO+uwv9Pjc6S3834Le03Tggv22zagInpTAZ+eydVjBcUzSovYWoSFhvzCi1aMeoDhDt+umnJJzbHeWJap3cYn2uFzvfIWE1rUU0rWtI48lXabsdkK4SZLvcwGcUdtQSyqsEp2jljjdNF1i3pmqdpH/pnp5ICe0cS52KLzG8Y58lrHysQE6di2FShcDfzVNqgTUYK5lYcovMhLBWMC6KsVX8VPgqSI0ZJ6uYQmDJSIeSwK+84gQQ6tq2ibiCMN0SskeDS/gkqQK4hpf858Ig3mY1L48PSX/YkQfpC1BhcwnSLo0m742Vq5iFxzMy+OUr4ZZ/KFZjdOC8sVeiMDIjzZteYsseDQo0uRdhcHfCwzo4rSnLCAjf7rv+VxlWzlHrZgljTG18Z2aaLAvPgMO4Bwk1au7j56z9qs6+oYAFkmGsMzB8zblQiB0DeNPCdwMlJmUDiyRsGUdisrZ16fdQRTJNpuFzRczGj/cYjl2hfFnZAHzCHkLSaZElJbZGchzUomp45FVyoJeBubQjkrXVDKs1r4WxfFcxsh79UV7rvA+8ieyooDKo8I2PHLNKdAFjTUYatONz+xURsoxK/2QPBt789v7h6gSb8EHZV2a71tvBNRkjfvkyjgf7wn89A+f1XsxWcYgSSfPGrlrNa2Xn30eTazcvo3YkkcOdAz04W1BDCxn/8oYs83FLeQwpWDLdrGYr3o/JYUN2eIhWuKkCyQ1YDezyCLphO1RXLKtVUwFBywY6s8mWbcJY3QlkXbI7Vt33LgSCK/6kWOD3XiFHC27ytMrDUE4tWczqW59AYV8nvMLQfPqK2Lq+9dJvHxfp7o3zJD7nvBG+uWppTs8QfLWOF/8VG0DDBv6pMFrujzT25K7qNcB0P4Ylxhl9ICIWtRbHgDMuOyg2oafY2lGO9ZxpYUiY5ARm4NxVmxHrWxeDSR/M8rdidGnL79MxsE v3RAFukN 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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 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(). David > > 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." > > Regards, > Eli >