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[80.230.68.31]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493c63bfba1sm156369225e9.15.2026.07.03.07.19.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2026 07:19:43 -0700 (PDT) Date: Fri, 3 Jul 2026 10:19:40 -0400 From: "Michael S. Tsirkin" To: Brett Sheffield Cc: Simon Schippers , regressions@lists.linux.dev, netdev@vger.kernel.org, Jakub Kicinski , Tim Gebauer , Willem de Bruijn , Jason Wang , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org Subject: Re: [REGRESSION][BISECTED] tun/tap & vhost-net: multi-threaded network performance Message-ID: <20260703101823-mutt-send-email-mst@kernel.org> References: <20260701165359-mutt-send-email-mst@kernel.org> <20260702185420-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: sgyj0_2GsyI2lgsgrXucEgOy0EVprZGjvbKJPPEL_7Y_1783088384 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jul 03, 2026 at 04:13:49PM +0200, Brett Sheffield wrote: > On 2026-07-02 18:55, Michael S. Tsirkin wrote: > > On Thu, Jul 02, 2026 at 01:07:47PM +0200, Brett Sheffield wrote: > > > On 2026-07-02 09:24, Simon Schippers wrote: > > > > On 7/1/26 22:56, Michael S. Tsirkin wrote: > > > > > - does it help to increase the tun queue size? > > > > > > > > I agree, this would be great to know. > > I tried adding a queue (qdisc pfifo limit 500) on both host and guest - no > apparent difference in drops or performance. > > If there's any other setting you want me to try, let me know. > > > Maybe it's the supposedly rare case? Does this change anything > > for you? > > I also tried both patches, but again, no noticable difference. > Thank you. Simon pointed out issues with the patches but he also said his intuition is strongly that it's not the way to go. Let's wait for him to post the backpressure patch, we'll see. -- MST