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([2620:10d:c092:600::1:72ea]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b77e216516sm10225969f8f.72.2025.07.29.01.52.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Jul 2025 01:52:11 -0700 (PDT) Message-ID: <7d7eb3cd-db7e-4a9e-8671-4185b716bbc8@gmail.com> Date: Tue, 29 Jul 2025 09:53:31 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm, page_pool: introduce a new page type for page pool in page type To: Byungchul Park Cc: Mina Almasry , linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, toke@redhat.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org References: <20250728052742.81294-1-byungchul@sk.com> <20250729010410.GC56089@system.software.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20250729010410.GC56089@system.software.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/29/25 02:04, Byungchul Park wrote: > On Mon, Jul 28, 2025 at 07:49:30PM +0100, Pavel Begunkov wrote: >> On 7/28/25 19:39, Mina Almasry wrote: >>> On Mon, Jul 28, 2025 at 11:35 AM Pavel Begunkov wrote: ...>>> This may be my bad since I said we should check if it's 0 initialized. >>> >>> It looks like on the devmem side as well we kvmalloc_array the niovs, >>> and if I'm checking through the helpers right, kvmalloc_array does >>> 0-initialize indeed. >> >> I wouldn't rely on that, it's just for zcrx I do: >> >> kvmalloc_array(..., GFP_KERNEL | __GFP_ZERO); > > For net_devmem_bind_dmabuf(), __GFP_ZERO will add bigger overhead than > just assignment, 'niov->pp = NULL'. That's not a place where you should care about zeroing overhead. > I'd like to ask you if you are still good with __GFP_ZERO overhead > before going ahead. However, it might be easier for you to just assign it directly for devmem and let Mina add GFP_ZERO if he fancy the idea. -- Pavel Begunkov