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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2076af252e2sm18901915ad.6.2024.09.12.16.09.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Sep 2024 16:09:49 -0700 (PDT) Date: Thu, 12 Sep 2024 16:09:48 -0700 From: Stephen Hemminger <stephen@networkplumber.org> To: Nandini Rangaswamy <nandini.rangaswamy@broadcom.com> Cc: Long Li <longli@microsoft.com>, "users@dpdk.org" <users@dpdk.org> Subject: Re: Netvsc vs Failsafe Performance Message-ID: <20240912160948.3714f01d@hermes.local> In-Reply-To: <CAAkQrK8uYciOV+-tgEvtGhE1UGTqyQ__zio1nVisXso6VfRp-g@mail.gmail.com> References: <CAAkQrK-quv_w+1KG=H3yDsiN9Xki9DigucZCy7q_RwMLmgCYyg@mail.gmail.com> <20240903170350.7e663864@hermes.local> <CAAkQrK-gvVUsdyK+EiuaWZk9U7-CRZaJXHAELbV5qjMzmMv82A@mail.gmail.com> <20240904154246.1c5bbb58@hermes.local> <PH0PR21MB4456D6BCB98F6E6F75D0D25DCE9D2@PH0PR21MB4456.namprd21.prod.outlook.com> <CAAkQrK8uYciOV+-tgEvtGhE1UGTqyQ__zio1nVisXso6VfRp-g@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 Thu, 12 Sep 2024 13:47:37 -0700 Nandini Rangaswamy <nandini.rangaswamy@broadcom.com> wrote: > Thanks for your response Long Li. > I see with netvsc the maximum number of Tx descriptors is restricted to > 4096 whereas the number of Rx descriptors is restricted to 8192. > But, for failsafe PMD , we see that both the number of Txd and Rxd is > restricted to 8192. > How is netvsc PMD giving the same performance as failsafe PMD ? > > Regards I think the limits there were somewhat arbitrary chose with netvsc. Don't remember a hard reason that would block larger sizes. Having really big rings won't help performance (i.e BufferBloat) and could a lot of memory consumption. When all heavy data traffic goes through the VF and that ring is different. Only DoS attacks should be impacted by rx/tx descriptor limits in the netvsc device. The linux driver actually has much smaller buffer.