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[146.241.228.125]) by smtp.gmail.com with ESMTPSA id a18-20020a0cefd2000000b005dd8b93456esm5340732qvt.6.2023.03.30.04.01.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 04:01:34 -0700 (PDT) Message-ID: Subject: Re: [PATCH net-next v2] net/core: add optional threading for backlog processing From: Paolo Abeni To: Jakub Kicinski , Felix Fietkau Cc: netdev@vger.kernel.org, Jonathan Corbet , "David S. Miller" , Eric Dumazet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 30 Mar 2023 13:01:31 +0200 In-Reply-To: <20230328161642.3d2f101c@kernel.org> References: <20230328195925.94495-1-nbd@nbd.name> <20230328161642.3d2f101c@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, 2023-03-28 at 16:16 -0700, Jakub Kicinski wrote: > On Tue, 28 Mar 2023 21:59:25 +0200 Felix Fietkau wrote: > > When dealing with few flows or an imbalance on CPU utilization, static = RPS > > CPU assignment can be too inflexible. Add support for enabling threaded= NAPI > > for backlog processing in order to allow the scheduler to better balanc= e > > processing. This helps better spread the load across idle CPUs. >=20 > Can you share some numbers vs a system where RPS only spreads to=20 > the cores which are not running NAPI? >=20 > IMHO you're putting a lot of faith in the scheduler and you need=20 > to show that it actually does what you say it will do. I have the same feeling. From your description I think some gain is possible if there are no other processes running except ksoftirq/rps/threaded napi.=C2=A0 I guess that the above is expect average state for a small s/w router, but if/when routing daemon/igmp proxy/local web server kicks-in you should notice a measurable higher latency (compared to plain RPS in the same scenario)??? Cheers, Paolo