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[81.185.174.106]) by smtp.gmail.com with ESMTPSA id i18sm10127049wrp.91.2019.07.12.09.48.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Jul 2019 09:48:30 -0700 (PDT) Subject: Re: [RFC PATCH net-next 0/3] net: batched receive in GRO path To: Edward Cree , Eric Dumazet , Paolo Abeni , David Miller Cc: netdev References: <7920e85c-439e-0622-46f8-0602cf37e306@solarflare.com> <677040f4-05d1-e664-d24a-5ee2d2edcdbd@solarflare.com> <1735314f-3c6a-45fc-0270-b90cc4d5d6ba@gmail.com> <4516a34a-5a88-88ef-e761-7512dff4f3ce@solarflare.com> <38ff0ce0-7e26-1683-90f0-adc9c0ac9abe@gmail.com> <927da9ee-c2fc-8556-fbeb-e26ea1c98d1e@solarflare.com> From: Eric Dumazet Message-ID: Date: Fri, 12 Jul 2019 18:48:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <927da9ee-c2fc-8556-fbeb-e26ea1c98d1e@solarflare.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/12/19 5:59 PM, Edward Cree wrote: > On 10/07/2019 18:39, Eric Dumazet wrote: >> Holding a small packet in the list up to the point we call busy_poll_stop() >> will basically make busypoll non working anymore. >> >> napi_complete_done() has special behavior when busy polling is active. > Yep, I get it now, sorry for being dumb :) > Essentially we're saying that things coalesced by GRO are 'bulk' traffic and >  can wait around, GRO can still be beneficial even when busypolling, since TCP stack will send a single ACK back, and a read()/recv() will copy the whole train instead of a single MSS. I should have mentioned that we have a patch that I forgot to upstream adding the PSH flag to all TSO packets, meaning the receiver can automatically learn the boundary of a GRO packet and not have to wait for the napi->poll() end (busypolling or not) > but the rest is the stuff we're polling for for low latency. > I'm putting a gro_normal_list() call after the trace_napi_poll() in >  napi_busy_loop() and testing that, let's see how it goes... >