From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Kiss Subject: Re: [Xen-devel] [PATCHv1 net] xen-netback: notify immediately after pushing Tx response. Date: Wed, 11 Mar 2015 17:09:04 +0000 Message-ID: <550076B0.3090404@linaro.org> References: <1426087679-13927-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: xen-devel@lists.xenproject.org, Wei Liu , Ian Campbell To: David Vrabel , netdev@vger.kernel.org Return-path: Received: from mail-we0-f172.google.com ([74.125.82.172]:41269 "EHLO mail-we0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751470AbbCKRJI (ORCPT ); Wed, 11 Mar 2015 13:09:08 -0400 Received: by wesw62 with SMTP id w62so10715092wes.8 for ; Wed, 11 Mar 2015 10:09:07 -0700 (PDT) In-Reply-To: <1426087679-13927-1-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On 11/03/15 15:27, David Vrabel wrote: > This fixes a performance regression introduced by > 7fbb9d8415d4a51cf542e87cf3a717a9f7e6aedc (xen-netback: release pending > index before pushing Tx responses) > > Moving the notify outside of the spin locks means it can be delayed a > long time (if the dealloc thread is descheduled or there is an > interrupt or softirq). > > Signed-off-by: David Vrabel Reviewed-by: Zoltan Kiss > --- > drivers/net/xen-netback/netback.c | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > index c4d68d7..7f8a466 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -96,6 +96,7 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx, > static void make_tx_response(struct xenvif_queue *queue, > struct xen_netif_tx_request *txp, > s8 st); > +static void push_tx_responses(struct xenvif_queue *queue); > > static inline int tx_work_todo(struct xenvif_queue *queue); > > @@ -655,15 +656,10 @@ static void xenvif_tx_err(struct xenvif_queue *queue, > unsigned long flags; > > do { > - int notify; > - > spin_lock_irqsave(&queue->response_lock, flags); > make_tx_response(queue, txp, XEN_NETIF_RSP_ERROR); > - RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify); > + push_tx_responses(queue); > spin_unlock_irqrestore(&queue->response_lock, flags); > - if (notify) > - notify_remote_via_irq(queue->tx_irq); > - > if (cons == end) > break; > txp = RING_GET_REQUEST(&queue->tx, cons++); > @@ -1655,7 +1651,6 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx, > { > struct pending_tx_info *pending_tx_info; > pending_ring_idx_t index; > - int notify; > unsigned long flags; > > pending_tx_info = &queue->pending_tx_info[pending_idx]; > @@ -1671,12 +1666,9 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx, > index = pending_index(queue->pending_prod++); > queue->pending_ring[index] = pending_idx; > > - RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify); > + push_tx_responses(queue); > > spin_unlock_irqrestore(&queue->response_lock, flags); > - > - if (notify) > - notify_remote_via_irq(queue->tx_irq); > } > > > @@ -1697,6 +1689,15 @@ static void make_tx_response(struct xenvif_queue *queue, > queue->tx.rsp_prod_pvt = ++i; > } > > +static void push_tx_responses(struct xenvif_queue *queue) > +{ > + int notify; > + > + RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify); > + if (notify) > + notify_remote_via_irq(queue->tx_irq); > +} > + > static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue, > u16 id, > s8 st, >