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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e72375b31sm212324345e9.20.2025.10.07.02.51.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Oct 2025 02:51:18 -0700 (PDT) Date: Tue, 7 Oct 2025 11:51:17 +0200 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH 3/5] tcp, flow: Replace per-connection in_epoll flag with epollfd in flow_common Message-ID: <20251007115117.3ba165a4@elisabeth> In-Reply-To: References: <20251003152717.2437765-1-lvivier@redhat.com> <20251003152717.2437765-4-lvivier@redhat.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: BMbCvNFF6dJstsLlIyyHMZVsTVsPdzVX4FfaZQalrvc_1759830680 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: 57DV2GXWV6U52UM7WOLMPPIVI2YH525B X-Message-ID-Hash: 57DV2GXWV6U52UM7WOLMPPIVI2YH525B X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Laurent Vivier , passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, 7 Oct 2025 17:07:37 +1100 David Gibson wrote: > On Fri, Oct 03, 2025 at 05:27:15PM +0200, Laurent Vivier wrote: > > The in_epoll boolean flag in tcp_tap_conn and tcp_splice_conn only tracked > > whether a connection was registered with epoll, not which epoll instance. > > This limited flexibility for future multi-epoll support. > > > > Replace the boolean with an epollfd field in flow_common that serves dual > > purpose: zero indicates not registered (replacing in_epoll=false), non-zero > > Don't use 0, since that's a valid fd. > > > stores the actual epoll fd (replacing in_epoll=true). > > I am a bit nervous about adding 31-bits to every flow, since I think > we're fairly close to a cacheline threshold. I mentioned to Laurent in our weekly call on Monday the same concern and that I would look into it (first step, I would say, actually check with pahole?) and, if it's an issue, into possible tricks to avoid making the struct too big. I still plan to do this. -- Stefano