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[87.12.139.105]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e80a63esm335385945e9.3.2026.04.03.03.04.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Apr 2026 03:04:18 -0700 (PDT) Date: Fri, 3 Apr 2026 12:04:12 +0200 From: Stefano Garzarella To: Laurence Rowe Cc: virtualization@lists.linux.dev, netdev@vger.kernel.org, Bobby Eshleman Subject: Re: [PATCH] vsock: avoid timeout for non-blocking accept() with empty backlog Message-ID: References: <20260402044637.73531-1-laurencerowe@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Apr 02, 2026 at 04:30:20PM -0700, Laurence Rowe wrote: >On Thu, Apr 2, 2026 at 12:22 PM Laurence Rowe wrote: >> >> On Thu, Apr 2, 2026 at 5:03 AM Stefano Garzarella wrote: >> >> > >Scheduling a timeout for a non-blocking accept with an empty backlog >> > >meant AF_VSOCK sockets used by epoll network servers incurred hundreds >> > >of microseconds of additional latency per accept loop compared to >> > >AF_INET or AF_UNIX sockets. >> > >> > Not related to this patch, but should we do something similar (in >> > another patch) also in vsock_connect() or doesn't matter since usually >> > it's always blocking? >> >> Looking at vsock_connect it's not immediately obvious to me whether it >> is affected >> in the same way. I'll capture some ftraces and follow up after >> updating this patch. > >This does not seem to be a problem for vsock_connect since it checks >for `if (flags & O_NONBLOCK) {` in the while loop before calling >`schedule_timeout`. > >Timings and ftraces: > >https://github.com/lrowe/linux-vsock-accept-timeout-investigation?tab=readme-ov-file#a-quick-look-at-connect Thanks for checking and for the fix! Stefano