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From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [net-next PATCH V2] virtio-net: switch to use XPS to choose txq
Date: Wed, 2 Oct 2013 09:15:45 +0300	[thread overview]
Message-ID: <20131002061545.GA6880@redhat.com> (raw)
In-Reply-To: <20130930.221040.543720988967287293.davem@davemloft.net>

On Mon, Sep 30, 2013 at 10:10:40PM -0700, David Miller wrote:
> From: Jason Wang <jasowang@redhat.com>
> Date: Mon, 30 Sep 2013 15:37:17 +0800
> 
> > We used to use a percpu structure vq_index to record the cpu to queue
> > mapping, this is suboptimal since it duplicates the work of XPS and
> > loses all other XPS functionality such as allowing use to configure
> > their own transmission steering strategy.
> > 
> > So this patch switches to use XPS and suggest a default mapping when
> > the number of cpus is equal to the number of queues. With XPS support,
> > there's no need for keeping per-cpu vq_index and .ndo_select_queue(),
> > so they were removed also.
> > 
> > Cc: Rusty Russell <rusty@rustcorp.com.au>
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> > Changes from V1:
> > - use cpumask_of() instead of allocate dynamically
> 
> This generates build warnings:
> 
> drivers/net/virtio_net.c: In function ‘virtnet_set_affinity’:
> drivers/net/virtio_net.c:1093:3: warning: passing argument 2 of ‘netif_set_xps_queue’ discards ‘const’ qualifier from pointer target type [enabled by default]
> In file included from drivers/net/virtio_net.c:20:0:
> include/linux/netdevice.h:2275:5: note: expected ‘struct cpumask *’ but argument is of type ‘const struct cpumask *’

Looks like we just need to tweak the signature there to const struct
cpumask *: it's never changed.

I just sent a patch
	[PATCH] netif_set_xps_queue: make cpu mask const
that does exactly that.

-- 
MST
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WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: jasowang@redhat.com, rusty@rustcorp.com.au,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [net-next PATCH V2] virtio-net: switch to use XPS to choose txq
Date: Wed, 2 Oct 2013 09:15:45 +0300	[thread overview]
Message-ID: <20131002061545.GA6880@redhat.com> (raw)
In-Reply-To: <20130930.221040.543720988967287293.davem@davemloft.net>

On Mon, Sep 30, 2013 at 10:10:40PM -0700, David Miller wrote:
> From: Jason Wang <jasowang@redhat.com>
> Date: Mon, 30 Sep 2013 15:37:17 +0800
> 
> > We used to use a percpu structure vq_index to record the cpu to queue
> > mapping, this is suboptimal since it duplicates the work of XPS and
> > loses all other XPS functionality such as allowing use to configure
> > their own transmission steering strategy.
> > 
> > So this patch switches to use XPS and suggest a default mapping when
> > the number of cpus is equal to the number of queues. With XPS support,
> > there's no need for keeping per-cpu vq_index and .ndo_select_queue(),
> > so they were removed also.
> > 
> > Cc: Rusty Russell <rusty@rustcorp.com.au>
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> > Changes from V1:
> > - use cpumask_of() instead of allocate dynamically
> 
> This generates build warnings:
> 
> drivers/net/virtio_net.c: In function ‘virtnet_set_affinity’:
> drivers/net/virtio_net.c:1093:3: warning: passing argument 2 of ‘netif_set_xps_queue’ discards ‘const’ qualifier from pointer target type [enabled by default]
> In file included from drivers/net/virtio_net.c:20:0:
> include/linux/netdevice.h:2275:5: note: expected ‘struct cpumask *’ but argument is of type ‘const struct cpumask *’

Looks like we just need to tweak the signature there to const struct
cpumask *: it's never changed.

I just sent a patch
	[PATCH] netif_set_xps_queue: make cpu mask const
that does exactly that.

-- 
MST

  reply	other threads:[~2013-10-02  6:15 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-30  7:37 [net-next PATCH V2] virtio-net: switch to use XPS to choose txq Jason Wang
2013-09-30  7:37 ` Jason Wang
2013-09-30  9:04 ` Michael S. Tsirkin
2013-09-30  9:04   ` Michael S. Tsirkin
2013-10-01  1:54   ` Rusty Russell
2013-10-01  1:54     ` Rusty Russell
2013-10-01  5:10 ` David Miller
2013-10-01  5:10   ` David Miller
2013-10-02  6:15   ` Michael S. Tsirkin [this message]
2013-10-02  6:15     ` Michael S. Tsirkin

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