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Tue, 03 Mar 2026 08:51:12 -0800 (PST) Received: from [192.168.1.102] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-899e53a16c0sm80399996d6.35.2026.03.03.08.51.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Mar 2026 08:51:11 -0800 (PST) Message-ID: <287ca341-13a4-4c8c-8bb2-e78dc019c7dc@kernel.dk> Date: Tue, 3 Mar 2026 09:51:05 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHSET 0/2] io_uring fixes To: Fiona Ebner , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, fam@euphon.net, stefanha@redhat.com, qemu-stable@nongnu.org References: <20260213143225.161043-1-axboe@kernel.dk> <3ba732d8-8e33-4bf3-af39-00360c39b940@proxmox.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <3ba732d8-8e33-4bf3-af39-00360c39b940@proxmox.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::730; envelope-from=axboe@kernel.dk; helo=mail-qk1-x730.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 3/3/26 4:52 AM, Fiona Ebner wrote: > Am 13.02.26 um 3:33 PM schrieb Jens Axboe: >> Hi, >> >> Patch 1 here is the real meat of this, patch 2 is just a slight >> improvement. For patch 1, it can literally yield a 50-80x improvement >> on the io_uring side for idle systems, where ppoll() ends up sleeping >> for 500 msec while there's IO to submit! I noticed this running the >> io_uring regression tests in a vm, where I use a variety of block >> devices for some of the tests. They would often randomly time out on >> AHCI devices, while running them on a virtio-blk or nvme device would >> finish in one second or so. I then wrote a reproducer to try and grok >> this and had claude dive into this, which helped me better grasp the >> various event loops. >> >> Please take a look and tell me what you think. Some variant of patch 1 >> should definitely be considered, but let me know if this is the right >> approach. I can easily test anything. >> >> Also note - this seems to trigger more easily or consistently on >> aarch64, which is where I run most of my local/immediate testing. >> >> util/fdmon-io_uring.c | 22 +++++++++++++++++++++- >> 1 file changed, 21 insertions(+), 1 deletion(-) >> > > CC-ing qemu-stable since this affects the 10.2 branch. The fixes are > already applied to master as > > 2ae361ef1d aio-posix: notify main loop when SQEs are queued > 961fcc0f22 fdmon-io_uring: check CQ ring directly in gsource_check Yes please, would be nice for them to hit the stable release(s) as well. Thanks Fiona! -- Jens Axboe