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b=Uk8LCrfdl+bpQBeTpDRh0oc+8+a48aSIelbqzRi4zcYvWLX8sL8PxBp5hbaMZ0N9Y nVwiwe5noR2fo5n8OoliuzsH7AN/eZRgcnZMxx4vJk4UrEIUqUa6k2idnbK9QgHqXj MvcdH/lQE7Be/UpQwxNPD6F6RDv4kQpNEWdShdefAKU7jb+xKA44rV4fWKT8iKCIpd oYq5git6zMaT/Ydsw25+f41mpCLw8kebEFGA22uBE3LXWKxb4zzlWHCYg2aA4NMASc 6KhnkAFxAiN3+HQ57h5wBLKt+VIJv0+/x3+ocfej2PJIAOaCgDGi2/izTJw36B81t0 qYENoTSEHp4mg== Date: Tue, 14 Jul 2026 15:24:56 +0300 From: Leon Romanovsky To: "Mike Rapoport (Microsoft)" Cc: Jason Gunthorpe , Dennis Dalessandro , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH v2 0/5] RDMA, IB: replace __get_free_pages() with kmalloc() Message-ID: <20260714122456.GD19233@unreal> References: <20260713-b4-rdma-v2-0-65d2a1a5180c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260713-b4-rdma-v2-0-65d2a1a5180c@kernel.org> X-Stat-Signature: dt7dkzno4tkf5b9emq9wen8ekcq8869j X-Rspamd-Queue-Id: 1484480009 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1784031899-611803 X-HE-Meta: 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 CbU7u6MR z9HUyKHU/1h/5asryTR+xFdIeBpDZ6W1LXXncTUNuWO2BXzGcFcIhWHLa4D3ikV9Ju6ypSj0x+1aVHFUz3GLx/YJYCLX1O3H4WsrjIB3xGs/fteZ2TfvnbhJ1DPscrKwp/7Dh63SwyZ4oZn1pl4uuB1NK/SLYj8JyTaNLfT60Ypgug13d+Mak4BMjQ9Ez63DVrQYUWAjkMdvOopqpfjqw8X542NOqs9nc4CafO5hUjWscoo/Gpb/hIdVzGMVzAlwS4ZncZ5lllrO8S/I+GCOJtNid7GLHG25cuEkj95yt4nX2rLzxO1FUqeGI8lJHUYpyBcOSjPXINo/znLJ3lPksezvfsAegdJIqX5N9G6LOG2W6FAngzN/gkELPgUy3c5HBcB6fabryE2RV6J5uu5M/ncMhS+amHoF7jiwGAiAoCV/O83s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 13, 2026 at 10:17:21AM +0300, Mike Rapoport (Microsoft) wrote: > This is a (small) part of larger work of replacing page allocator calls > with kmalloc. > > My initial intention a few month ago was to remove ugly casts [1], but then > willy pointed out that Linus objected to something like this [2] and it > looks like more than a decade old technical debt. > > Largely, anything that doesn't need struct page (or a memdesc in the > future) should just use kmalloc() or kvmalloc() to allocate memory. > kmalloc() guarantees alignment, physical contiguity and working > virt_to_phys() and beside nicer API that returns void * on alloc and > doesn't require to know the allocation size on free, kmalloc() provides > better debugging capabilities than page allocator. > > Another thing is that touching these allocation sites gives the reviewers > opportunity to see if a PAGE_SIZE buffer is actually needed or maybe > another size is appropriate. > > For larger allocations that don't need physically contiguous memory > kvmalloc() can be a better option that __get_free_pages() because under > memory pressure it's is easier to allocate several order-0 pages than a > physically contiguous chunk with the same number of pages. > > And last, but not least, removing needless calls to page allocator should > help with memdesc (aka project folio) conversion. There will be way less > places to audit to see if the user was actually using struct page. > > Also in git: > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/rdma Will you also change get_zeroed_page() in RDMA, or should I prepare a patch? Thanks > > [1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@kernel.org/ > [2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@mail.gmail.com/ > > --- > v2 changes: > * add comment to keep markers for sites that need "fast and as large as > possible" allocation helper > > v1: https://patch.msgid.link/20260630-b4-rdma-v1-0-ab42bcf0de92@kernel.org > > --- > Mike Rapoport (Microsoft) (5): > RDMA/umem: ib_umem_get(): use kmalloc() to allocate page array > RDMA/mlx5: replace __get_free_page() with kmalloc() > IB/mthca: mthca_reg_user_mr(): use kmalloc() to allocate addresses array > IB/mthca: allocate mthca_array memory with kzalloc() > IB/rdmavt: use kzalloc() to allocate QPN-map pages > > drivers/infiniband/core/umem.c | 5 +++-- > drivers/infiniband/hw/mlx5/odp.c | 6 ++++-- > drivers/infiniband/hw/mthca/mthca_allocator.c | 6 +++--- > drivers/infiniband/hw/mthca/mthca_provider.c | 5 +++-- > drivers/infiniband/sw/rdmavt/qp.c | 8 ++++---- > 5 files changed, 17 insertions(+), 13 deletions(-) > --- > base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 > change-id: 20260610-b4-rdma-44625922fe16 > > -- > Sincerely yours, > Mike. >