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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-479311ee44csm226218045e9.14.2025.12.08.00.22.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Dec 2025 00:22:07 -0800 (PST) Date: Mon, 8 Dec 2025 09:22:05 +0100 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH v2 0/9] tcp: Fix throughput issues with non-local peers Message-ID: <20251208092205.14060704@elisabeth> In-Reply-To: References: <20251208002229.391162-1-sbrivio@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: wUVSi9HsKtYyyia4k9FjLFgN0LymD97MtFfRLhvJMk8_1765182128 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: WUWJERSWXEAPQX56H5ILYDMDJDD5QZ5J X-Message-ID-Hash: WUWJERSWXEAPQX56H5ILYDMDJDD5QZ5J 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: passt-dev@passt.top, Max Chernoff 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 Mon, 8 Dec 2025 17:46:43 +1100 David Gibson wrote: > On Mon, Dec 08, 2025 at 01:22:08AM +0100, Stefano Brivio wrote: > > Patch 2/9 is the most relevant fix here, as we currently advertise a > > window that might be too big for what we can write to the socket, > > causing retransmissions right away and occasional high latency on > > short transfers to non-local peers. > > > > Mostly as a consequence of fixing that, we now need several > > improvements and small fixes, including, most notably, an adaptive > > approach to pick the interval between checks for socket-side ACKs > > (patch 3/9), and several tricks to reliably trigger TCP buffer size > > auto-tuning as implemented by the Linux kernel (patches 5/9 and 7/9). > > > > These changes make some existing issues more relevant, fixed by the > > other patches. > > I've made a number of comments through the series. I think they do > want some consideration. But given this works to address a real > problem empirically, I'm fine for this to be merged as is, with more > polishing later. I just posted v3 addressing a few items that actually look wrong / problematic to me. Note that I forgot to change the "scaling" function name later in the series (as posted), I'm fixing it up on merge. -- Stefano