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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id d10sm1577096ejw.125.2021.04.22.03.48.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Apr 2021 03:48:15 -0700 (PDT) Date: Thu, 22 Apr 2021 12:48:13 +0200 From: Stefano Garzarella To: Arseny Krasnov Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jorgen Hansen , Colin Ian King , Andra Paraschiv , Norbert Slusarek , Alexander Popov , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "stsp2@yandex.ru" , "oxffffaa@gmail.com" Subject: Re: [RFC PATCH v8 00/19] virtio/vsock: introduce SOCK_SEQPACKET support Message-ID: <20210422104813.e2p4wzuk2ahw7af7@steredhat> References: <20210413123954.3396314-1-arseny.krasnov@kaspersky.com> <20210421095213.25hnfi2th7gzyzt2@steredhat> <2c3d0749-0f41-e064-0153-b6130268add2@kaspersky.com> <20210422084638.bvblk33b4oi6cec6@steredhat> <20210422100217.jmpgevtrukqyukfo@steredhat> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Apr 22, 2021 at 01:29:54PM +0300, Arseny Krasnov wrote: > >On 22.04.2021 13:02, Stefano Garzarella wrote: >> On Thu, Apr 22, 2021 at 12:40:17PM +0300, Arseny Krasnov wrote: >>> On 22.04.2021 11:46, Stefano Garzarella wrote: >>>> On Wed, Apr 21, 2021 at 06:06:28PM +0300, Arseny Krasnov wrote: >>>>> Thank You, i'll prepare next version. Main question is: does this >>>>> approach(no SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id') considered >>>>> good? In this case it will be easier to prepare final version, because >>>>> is smaller and more simple than previous logic. Also patch to spec >>>>> will be smaller. >>>> Yes, it's definitely much better than before. >>>> >>>> The only problem I see is that we add some overhead per fragment >>>> (header). We could solve that with the mergeable buffers that Jiang is >>>> considering for DGRAM. >>> If we are talking about receive, i think, i can reuse merge logic for >> Yep, for TX the guest can potentially enqueue a big buffer. >> Maybe it's still worth keeping a maximum size and fragmenting as we do >> now. >> >>> stream sockets, the only difference is that buffers are mergeable >>> until previous EOR(e.g. previous message) bit is found in rx queue. >>> >> I got a little lost. >> Can you elaborate more? > >I'm talking about 'virtio_transport_recv_enqueue()': it tries to copy > >data of new packet to buffer of tail packet in rx queue. In case of > >SEQPACKET i can reuse it, just adding logic that check EOR bit of > >tail packet. This might be a good idea. It doesn't save us the transmitted header though, but at least it saves us from queuing it. Even if with SEQPACKET I don't expect small packets, since it's the driver that divides them and I think it does everything to use the maximum available. Instead the mergeable buffers I was referring to are based on the virito-net feature VIRTIO_NET_F_MRG_RXBUF. Jiang is investigating whether we can reuse them for DGRAM. Thanks, Stefano