From: Stephen Hemminger <stephen@networkplumber.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: davem@davemloft.net, kys@microsoft.com, netdev@vger.kernel.org,
Stephen Hemminger <sthemmin@microsoft.com>
Subject: Re: [PATCH 18/18] netvsc: call netif_receive_skb
Date: Tue, 24 Jan 2017 15:00:28 -0800 [thread overview]
Message-ID: <20170124150028.4981db42@xeon-e3> (raw)
In-Reply-To: <1485297559.16328.343.camel@edumazet-glaptop3.roam.corp.google.com>
On Tue, 24 Jan 2017 14:39:19 -0800
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Tue, 2017-01-24 at 13:06 -0800, Stephen Hemminger wrote:
> > To improve performance, netvsc can call network stack directly and
> > avoid the local backlog queue. This is safe since incoming packets are
> > handled in softirq context already because the receive function
> > callback is called from a tasklet.
>
> Is this tasklet implementing a limit or something ?
The ring only holds a fixed amount of data so there is a limit but
it is quite large.
>
> netif_rx() queues packets to the backlog, which is processed later by
> net_rx_action() like other NAPI, with limit of 64 packets per round.
Since netvsc_receive has to copy all incoming data it is a bottleneck
unto itself. By the time net_rx_action is invoked the cache is stale.
>
> Calling netif_receive_skb() means you can escape this ability to fairly
> distribute the cpu cycles among multiple NAPI.
>
> I do not see range_cnt being capped in netvsc_receive()
There is no cap. NAPI is coming and will help.
next prev parent reply other threads:[~2017-01-24 23:00 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 21:05 [PATCH net-next 00/18] netvsc driver enhancements for net-next Stephen Hemminger
2017-01-24 21:05 ` [PATCH 01/18] netvsc: remove no longer needed receive staging buffers Stephen Hemminger
2017-01-24 21:05 ` [PATCH 02/18] netvsc: negotiate checksum and segmentation parameters Stephen Hemminger
2017-01-24 21:06 ` [PATCH 03/18] netvsc: report number of rx queues in ethtool Stephen Hemminger
2017-01-24 21:06 ` [PATCH 04/18] netvsc: report rss field values Stephen Hemminger
2017-01-24 21:06 ` [PATCH 05/18] netvsc: add ethtool ops to get/set RSS key Stephen Hemminger
2017-01-24 21:06 ` [PATCH 06/18] netvsc: allow more flexible setting of number of channels Stephen Hemminger
2017-01-24 21:06 ` [PATCH 07/18] netvsc: allow get/set of RSS indirection table Stephen Hemminger
2017-01-24 21:06 ` [PATCH 08/18] netvsc: enhance transmit select_queue Stephen Hemminger
2017-01-24 21:06 ` [PATCH 09/18] netvsc: remove unused variables Stephen Hemminger
2017-01-24 21:06 ` [PATCH 10/18] netvsc: group all per-channel state together Stephen Hemminger
2017-01-24 21:06 ` [PATCH 11/18] netvsc: optimize receive path Stephen Hemminger
2017-01-24 21:06 ` [PATCH 12/18] netvsc: don't pass void * to internal device_add Stephen Hemminger
2017-01-24 21:06 ` [PATCH 13/18] netvsc: simplify rndis_filter_remove Stephen Hemminger
2017-01-24 21:06 ` [PATCH 14/18] netvsc: eliminate per-device outstanding send counter Stephen Hemminger
2017-01-24 21:06 ` [PATCH 15/18] netvsc: account for packets/bytes transmitted after completion Stephen Hemminger
2017-01-24 21:06 ` [PATCH 16/18] netvsc: report per-channel stats in ethtool statistics Stephen Hemminger
2017-01-24 21:06 ` [PATCH 17/18] netvsc: simplify get next send section Stephen Hemminger
2017-01-24 21:06 ` [PATCH 18/18] netvsc: call netif_receive_skb Stephen Hemminger
2017-01-24 22:39 ` Eric Dumazet
2017-01-24 23:00 ` Stephen Hemminger [this message]
2017-01-24 23:07 ` Eric Dumazet
2017-01-24 21:30 ` [PATCH net-next 00/18] netvsc driver enhancements for net-next David Miller
2017-01-24 22:00 ` Stephen Hemminger
2017-01-24 22:50 ` Stephen Hemminger
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