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[82.57.51.170]) by smtp.gmail.com with ESMTPSA id q21-20020ac87355000000b003e387a2fbdfsm2158689qtp.0.2023.03.22.07.41.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 07:41:19 -0700 (PDT) Date: Wed, 22 Mar 2023 15:41:15 +0100 From: Stefano Garzarella To: Arseniy Krasnov Cc: Stefan Hajnoczi , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Bobby Eshleman , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru, oxffffaa@gmail.com Subject: Re: [RFC PATCH v4] virtio/vsock: allocate multiple skbuffs on tx Message-ID: <20230322144115.sz3icgbnhjgae2fj@sgarzare-redhat> References: <0e0c1421-7cdc-2582-b120-cad6f42824bb@sberdevices.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <0e0c1421-7cdc-2582-b120-cad6f42824bb@sberdevices.ru> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 21, 2023 at 06:03:14PM +0300, Arseniy Krasnov wrote: >This adds small optimization for tx path: instead of allocating single >skbuff on every call to transport, allocate multiple skbuff's until >credit space allows, thus trying to send as much as possible data without >return to af_vsock.c. > >Signed-off-by: Arseniy Krasnov >--- > Link to v1: > https://lore.kernel.org/netdev/2c52aa26-8181-d37a-bccd-a86bd3cbc6e1@sberdevices.ru/ > Link to v2: > https://lore.kernel.org/netdev/ea5725eb-6cb5-cf15-2938-34e335a442fa@sberdevices.ru/ > Link to v3: > https://lore.kernel.org/netdev/f33ef593-982e-2b3f-0986-6d537a3aaf08@sberdevices.ru/ > > Changelog: > v1 -> v2: > - If sent something, return number of bytes sent (even in > case of error). Return error only if failed to sent first > skbuff. > > v2 -> v3: > - Handle case when transport callback returns unexpected value which > is not equal to 'skb->len'. Break loop. > - Don't check for zero value of 'rest_len' before calling > 'virtio_transport_put_credit()'. Decided to add this check directly > to 'virtio_transport_put_credit()' in separate patch. > > v3 -> v4: > - Use WARN_ONCE() to handle case when transport callback returns > unexpected value. > - Remove useless 'ret = -EFAULT;' assignment for case above. > > net/vmw_vsock/virtio_transport_common.c | 59 +++++++++++++++++++------ > 1 file changed, 45 insertions(+), 14 deletions(-) > >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >index 6564192e7f20..a300f25749ea 100644 >--- a/net/vmw_vsock/virtio_transport_common.c >+++ b/net/vmw_vsock/virtio_transport_common.c >@@ -196,7 +196,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > const struct virtio_transport *t_ops; > struct virtio_vsock_sock *vvs; > u32 pkt_len = info->pkt_len; >- struct sk_buff *skb; >+ u32 rest_len; >+ int ret; > > info->type = virtio_transport_get_type(sk_vsock(vsk)); > >@@ -216,10 +217,6 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > > vvs = vsk->trans; > >- /* we can send less than pkt_len bytes */ >- if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) >- pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE; >- > /* virtio_transport_get_credit might return less than pkt_len credit */ > pkt_len = virtio_transport_get_credit(vvs, pkt_len); > >@@ -227,17 +224,51 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW) > return pkt_len; > >- skb = virtio_transport_alloc_skb(info, pkt_len, >- src_cid, src_port, >- dst_cid, dst_port); >- if (!skb) { >- virtio_transport_put_credit(vvs, pkt_len); >- return -ENOMEM; >- } >+ ret = 0; nit: this initialization seems superfluous since `ret` is overwritten later ... >+ rest_len = pkt_len; >+ >+ do { >+ struct sk_buff *skb; >+ size_t skb_len; >+ >+ skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len); >+ >+ skb = virtio_transport_alloc_skb(info, skb_len, >+ src_cid, src_port, >+ dst_cid, dst_port); >+ if (!skb) { >+ ret = -ENOMEM; >+ break; >+ } > >- virtio_transport_inc_tx_pkt(vvs, skb); >+ virtio_transport_inc_tx_pkt(vvs, skb); > >- return t_ops->send_pkt(skb); >+ ret = t_ops->send_pkt(skb); ... here. >+ nit: we can remove this extra line >+ if (ret < 0) >+ break; >+ >+ /* Both virtio and vhost 'send_pkt()' returns 'skb_len', >+ * but for reliability use 'ret' instead of 'skb_len'. >+ * Also if partial send happens (e.g. 'ret' != 'skb_len') >+ * somehow, we break this loop, but account such returned >+ * value in 'virtio_transport_put_credit()'. >+ */ >+ rest_len -= ret; >+ >+ if (WARN_ONCE(ret != skb_len, >+ "'send_pkt()' returns %i, but %zu expected\n", >+ ret, skb_len)) >+ break; >+ } while (rest_len); >+ >+ virtio_transport_put_credit(vvs, rest_len); >+ >+ /* Return number of bytes, if any data has been sent. */ >+ if (rest_len != pkt_len) >+ ret = pkt_len - rest_len; >+ >+ return ret; > } > > static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, >-- 2.25.1 > The patch LGTM: Reviewed-by: Stefano Garzarella Anyway, feel free to include in the same series or as separate patch also the changes to avoid useless lock in virtio_transport_put_credit() and virtio_transport_get_credit(). I would include it in this series, because before these changes, we used to call virtio_transport_put_credit() only in the error path, while now we always call it, even when rest_len is 0. Thanks, Stefano