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b=Yk3s3d9frEWJZPF2MxjOZchcesGfDugA5BuxyDVBmApifp1nrXdBpEzCpJH135Z6v pGzHY0gQfwXYmSiHDmNGG3fWlgsrAVtTUjAgEKgTx+LSJq1LxyCnWmYQK598Fy7BNJ mgdd5EvGuaW1u0OeZ1SxXFAJnBEWulBCMtEpZEE8NzIETSir8TkiU4PYPuX7zsN/cS gvCwafWEipxdq2SZNqRTVIZMR4gtnUoPMtw8wUxI2SLTH0dYcSun490m/D2NhyjRMn LUYAQV+T8Fotdet4iYmRu+ol0wEuPD/vicVi+vMhVpVwFJO7zx1mOW9LpqdhrBtznQ HTzwwcKy85ODA== Date: Mon, 9 Nov 2026 12:10:59 +0200 From: Mike Rapoport To: Juergen Gross Cc: Stefano Stabellini , Oleksandr Tyshchenko , David Hildenbrand , Vlastimil Babka , linux-mm@kvack.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] xen/events: replace __get_free_pages() with kmalloc() Message-ID: References: <20261108-b4-xen-v1-1-76095f25cbf4@kernel.org> <7af392b9-0cf9-46fe-a820-c994942893fe@suse.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7af392b9-0cf9-46fe-a820-c994942893fe@suse.com> X-Rspamd-Server: rspam06 X-Stat-Signature: xb9fcy1pe348pt87xia937ob4n33hxq8 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: ECFB7180003 X-Rspam-User: X-HE-Tag: 1794219065-154329 X-HE-Meta: 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 dHbGebuv U3fFQ5YLZ7ppOo7aYGbZjgS9UNB3X/LHSZIaN1TgxWrcV8iZDLFFl8dT/qjs5TIVP993V6aODERrgo4wP9Nd6XI5cDW88wp29M/FJ16y70oaBbiHCJPLFiQdDKDV2N8C0Hp+Pisb7LRwovOSiXFIMn/4gUvKfaYbePcQdC58GA0rBeV1MrdhZWRBWfL1dkSfHkWhH6WHitWet3R+WpgBh2TlFWGgEdFVNfTh4uHpM47ihFOf+OkkUJ/FT0R3Rc/dJDi+jXhRfgz6lCfNKezdjIp9QT9JJXOs+aM2KqweimWW3/PJwrGLSrQsMOct/muxD+RH/e1zPgHuuRIuWfLEMv/FFjA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Nov 09, 2026 at 08:53:18AM +0100, Juergen Gross wrote: > On 08.11.26 09:42, Mike Rapoport (Microsoft) wrote: > > set_evtchn_to_irq() allocates a page for the event channel to IRQ > > number software lookup table. > > > > This buffer can be allocated with kmalloc() as there's nothing special > > about it to go directly to the page allocator. > > > > kmalloc() provides a better API that does not require ugly casts and > > kfree() does not need to know the size of the freed object. > > > > Performance difference between kmalloc() and __get_free_pages() is not > > measurable as both allocators take an object/page from a per-CPU list for > > fast path allocations. > > > > For the slow path the performance is anyway determined by the amount of > > reclaim involved rather than by what allocator is used. > > > > Replace use of __get_free_pages() with kmalloc() and free_pages() with > > kfree(). > > > > Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com > > Signed-off-by: Mike Rapoport (Microsoft) > > Shouldn't you also replace __get_free_page() in xen_init_IRQ()? I don't see > why this is being omitted. Just an overlook, will send v2 with this too. > Juergen -- Sincerely yours, Mike.