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b=I6lqx7xe7ArEoBeN2UysBFuosgjtJd5J+5+JeOIu7nS7HkHEgOhZKD+NYpCgObeHQ yx2gWe6NnthkQSUTweAI36dYEHA14aVvXYEOst62rLvNCjMo1jTB8pbeCqQzyQJzGh dEuhY/mgrlzj09HUZxkcxAwvKcS/G95M7h8YF6EN5a3vmMQWrodWMlnCJnCcW+OlGf ehGlUmxiDsExBPFzuMKvrjJdu1MxfULg8BOK1azZFEExpSBfKc+/rNWw7bQQAuNtXG DrymVoUdkO1du/sPhAAjdKEL71Rpaih6H9vUFDqbg/ndhd54OWQjJCJJYfXrmFzny/ hmv0rm2Hnf/kw== Date: Tue, 30 Jun 2026 18:01:17 +0300 From: Mike Rapoport To: Jason Gunthorpe , Vlastimil Babka Cc: Leon Romanovsky , Dennis Dalessandro , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH 1/5] RDMA/umem: ib_umem_get(): use kmalloc() to allocate page array Message-ID: References: <20260630-b4-rdma-v1-0-ab42bcf0de92@kernel.org> <20260630-b4-rdma-v1-1-ab42bcf0de92@kernel.org> <20260630123150.GB7525@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 70E8C1C000D X-Rspam-User: X-Stat-Signature: 3d66cs8yasu8bsw4g9cqujaktdinndo5 X-HE-Tag: 1782831684-637859 X-HE-Meta: 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 pL96SBqN qX7UpfjagnecWFypDjrO4WwWs9N+0qCaYGExtNx6v46kjiW6Mde73vBNLcigm2gzuxvPm9fSAUJobWKi17R67vYhlZaLDzC6yRCMo/mX32h7vXfPXbSfXcsKbNQIpb9EdEy6G6nDNiJZKBYjTsaQTDDiMwTZteQtODEDidnFYhWaIhxAswLJCynWtX6U0Ebj+I+B8gpYMYIymvnOquwABeHkJbXsiwQ/jICCqHOGopFrVVGlwJMbD4nnxQr19DVaDK5A3JdnwVXm7w6Xja7mn/SoDh0vLaGPAmqKHUlFiBfZKQQk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: (actually adding Vlastimil :) ) On Tue, Jun 30, 2026 at 06:00:24PM +0300, Mike Rapoport wrote: > (adding Vlastimil) > > On Tue, Jun 30, 2026 at 09:31:50AM -0300, Jason Gunthorpe wrote: > > On Tue, Jun 30, 2026 at 01:52:29PM +0300, Mike Rapoport (Microsoft) wrote: > > > ib_umem_get() allocates an array of pointers to struct page for > > > pin_user_pages_fast() calls during memory registration. > > > > A whole bunch of these use cases in rdma are really "give me some > > temporary memory, I want it fast and as large as possible. In a > > syscall context I will free it before returning back to userspace" > > Not sure I follow where "as large as possible" comes from. Here it's > explicitly a page. > > And does "fast" mean that vmalloc() is not an option? > > > eg we'd be really happy to get any kind of high order page here. > > > > So, how would you feel about a new API? > > > > void *kmalloc_temporary(size_t min_size, size_t max_size, size_t *actual_size, gfp); > > > > I know of a few other cases like this in the kernel at least. > > > > The implementation could try to find an available high order page and > > immediately return it, otherwise do a small reclaim allocation? > > How do you suggest to decide how much of reclaim should happen? With the > usual semantics of gfp? > > > Jason > > -- > Sincerely yours, > Mike. -- Sincerely yours, Mike.