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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-736c9ba6c37sm4046504b3a.159.2025.03.10.14.25.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Mar 2025 14:25:01 -0700 (PDT) Date: Mon, 10 Mar 2025 14:24:57 -0700 From: Stephen Hemminger <stephen@networkplumber.org> To: Mikhail Malofeev <mdmalofeev@gmail.com> Cc: users@dpdk.org Subject: Re: DPDK multiprocessing issue: what if primary process dies Message-ID: <20250310142457.424318f4@hermes.local> In-Reply-To: <CAF6DLt681eC8J-EUFCKJsTOVpSG0naO24NSvA1CO0_Y6fbvw4w@mail.gmail.com> References: <CAF6DLt681eC8J-EUFCKJsTOVpSG0naO24NSvA1CO0_Y6fbvw4w@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: users@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK usage discussions <users.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/users>, <mailto:users-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/users/> List-Post: <mailto:users@dpdk.org> List-Help: <mailto:users-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/users>, <mailto:users-request@dpdk.org?subject=subscribe> Errors-To: users-bounces@dpdk.org On Mon, 10 Mar 2025 17:29:09 +0100 Mikhail Malofeev <mdmalofeev@gmail.com> wrote: > Hello everyone, > > I am new to DPDK and I am implementing a DPDK-based application which might > be running as a multi-process application. My understanding is that one of > the processes should be the primary one, responsible for initializing and > managing the hugepages. All the other processes should be secondary, > meaning that they are connected to the primary process during DPDK > initialization to get information about hugepages (please correct me if I > am mistaken here). That is one usage model. But secondary processes add additional overhead and are certainly not required. > I am interested in the scenario where there are multiple DPDK processes, > and the primary process dies. As far as I understand, existing secondary > processes will continue running; however, I will not be able to start new > DPDK processes: Once primary process dies, the DPDK application is not in a viable state. The most common model is to use a service manager (like systemd) to recover if primary process dies. The secondary processes should all be monitoring for notification that the primary dies, and exit then. > 1) I cannot start a new primary process because it will try to initialize > hugepages and this will fail since some of them are in use by existing > secondary processes (source: > https://stackoverflow.com/questions/74602244/dpdk-multi-process-kill-a-primary-process-and-restart-as-a-secondary-doesnt-wo > ) > 2) I cannot start a new secondary process because there is no primary > process to connect to and get the hugepages info, so the secondary process > won't be able to complete the initialization. > > Hence, if my primary process terminates, what should I do in order to start > it again? > > I have come up with two possible solutions: > 1) If the primary process dies, I will have to kill all the secondary > processes and restart everything. This solution is not ideal because I want > to minimize the amount of time when processes are not running. > 2) Have a dummy primary process that does not contain any critical business > logic and is solely responsible for DPDK initialization. Then, all the > business-critical applications must be secondary processes. If one of them > dies, I can simply restart it without interrupting other processes. This > solution sounds better than the first, but it is still not perfect as it > requires running an additional dummy process which I would prefer to avoid. > > Could anyone please advise me on the idiomatic way of dealing with these > multiprocessing issues? > Use systemd, and do full restart.