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Thu, 5 Jun 2025 15:35:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id a0amBl65QWi5YQAAD6G6ig (envelope-from ); Thu, 05 Jun 2025 15:35:58 +0000 Message-ID: <154aa365-0e27-458c-b801-62fd1cbfa169@suse.de> Date: Thu, 5 Jun 2025 17:35:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/4] fbdev/deferred-io: Support contiguous kernel memory framebuffers To: Michael Kelley , Simona Vetter Cc: David Hildenbrand , "simona@ffwll.ch" , "deller@gmx.de" , "haiyangz@microsoft.com" , "kys@microsoft.com" , "wei.liu@kernel.org" , "decui@microsoft.com" , "akpm@linux-foundation.org" , "weh@microsoft.com" , "hch@lst.de" , "dri-devel@lists.freedesktop.org" , "linux-fbdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "linux-mm@kvack.org" References: <20250523161522.409504-1-mhklinux@outlook.com> <20250523161522.409504-4-mhklinux@outlook.com> <9a93813c-4d7c-45ef-b5a2-0ad37e7a078a@suse.de> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8A7BA18000B X-Stat-Signature: kmr4ci3q1hccr9trgyjyu4o8yhao7pxw X-Rspam-User: X-HE-Tag: 1749137760-905253 X-HE-Meta: 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 yBMRSNeW vw7rjz7klHfVlqkFdWEccZ5f7LBHeE+J5EPMITiyqfAvznUc4SyqbMkleBTplPJMPQG5kIqwpLlylYwP33UpVy5k4Xx0nDkxAqRXADWEhaMKr9pBJoC79jyO0ZO4tVuVwGhueCOHk5s8lrX96Kl65liy0dY1SXU8xjW1QJWw+DESjCr/T8Z9pIuGOG0yh2rvnm3Opd5fgKUC4wO/N+wutH+xPfPQ6X0T15OcZp+wN022spttPtAV6r0iNblaZjcOK2DkD2iSKPtTPMUZF9UDVu1gpRUUCQqZBIA6HewEFi0AAnlYGmxefmEU1LdvrSwxbm+/PeM2XPeGgZlGuGQLvZHskHtRnCQ5O5aGkD4C8pQKH0potXEMkdAL5FA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Am 04.06.25 um 23:43 schrieb Michael Kelley: [...] > Nonetheless, there's an underlying issue. A main cause of the difference > is the number of messages to Hyper-V to update dirty regions. With > hyperv_fb using deferred I/O, the messages are limited 20/second, so > the total number of messages to Hyper-V is about 480. But hyperv_drm > appears to send 3 messages to Hyper-V for each line of output, or a total of > about 3,000,000 messages (~90K/second). That's a lot of additional load > on the Hyper-V host, and it adds the 10 seconds of additional elapsed > time seen in the guest. There also this ugly output in dmesg because the > ring buffer for sending messages to the Hyper-V host gets full -- Hyper-V > doesn't always keep up, at least not on my local laptop where I'm > testing: > > [12574.327615] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12574.327684] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12574.327760] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12574.327841] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12597.016128] hyperv_sendpacket: 6211 callbacks suppressed > [12597.016133] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12597.016172] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12597.016220] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > [12597.016267] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] *ERROR* Unable to send packet via vmbus; error -11 > > hyperv_drm could be fixed to not output the ugly messages, but there's > still the underlying issue of overrunning the ring buffer, and excessively > hammering on the host. If we could get hyperv_drm doing deferred I/O, I > would feel much better about going full-on with deprecating hyperv_fb. I try to address the problem with the patches at https://lore.kernel.org/dri-devel/20250605152637.98493-1-tzimmermann@suse.de/ Testing and feedback is much appreciated. Best regards Thomas > > Michael > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)