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Date: Fri, 24 Sep 2010 09:07:29 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Ben Hutchings <bhutchings@...arflare.com>,
Tom Herbert <therbert@...gle.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
linux-net-drivers@...arflare.com, Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH net-next-2.6] rps: allocate rx queues in
register_netdevice only
Le vendredi 24 septembre 2010 à 05:26 +0200, Eric Dumazet a écrit :
> > Also, I dont understand why we need to restrict
> > netif_set_real_num_rx_queues() to lower the count.
> > This wastes memory.
> >
> > Why dont we allocate dev->_rx once we know the real count, not in
> > alloc_netdev_mq() but in register_netdevice() ?
> >
> >
>
> Here is a patch to make this possible
>
> I guess a similar thing could be done for tx queues.
>
> boot tested, but please double check.
>
> Thanks
>
> [PATCH net-next-2.6] rps: allocate rx queues in register_netdevice()
>
> Instead of having two places were we allocate dev->_rx, introduce
> netif_alloc_rx_queues() helper and call it only from
> register_netdevice(), not from alloc_netdev_mq()
>
> Goal is to let drivers change dev->num_rx_queues after allocating netdev
> and before registering it.
>
> This also removes a lot of ifdefs in net/core/dev.c
>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
> net/core/dev.c | 76 +++++++++++++++++++----------------------------
> 1 file changed, 32 insertions(+), 44 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 2c7934f..9110b8d 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4964,6 +4964,34 @@ void netif_stacked_transfer_operstate(const struct net_device *rootdev,
> }
> EXPORT_SYMBOL(netif_stacked_transfer_operstate);
>
> +static int netif_alloc_rx_queues(struct net_device *dev)
> +{
> +#ifdef CONFIG_RPS
> + unsigned int i, count = dev->num_rx_queues;
> +
Tom
I tried to find a caller with dev->num_rx_queues = 0, but failed
If it's valid, we might add a
if (!dev->num_rx_queues)
dev->num_rx_queues = 1;
I wonder if you remember why you added the section :
/*
* Allocate a single RX queue if driver never called
* alloc_netdev_mq
*/
>
>
> + if (count) {
> + struct netdev_rx_queue *rx;
> +
> + rx = kcalloc(count, sizeof(struct netdev_rx_queue), GFP_KERNEL);
> + if (!rx) {
> + pr_err("netdev: Unable to allocate %u rx queues.\n",
> + count);
> + return -ENOMEM;
> + }
> + dev->_rx = rx;
> + atomic_set(&rx->count, count);
> +
> + /*
> + * Set a pointer to first element in the array which holds the
> + * reference count.
> + */
> + for (i = 0; i < count; i++)
> + rx[i].first = rx;
> + }
> +#endif
> + return 0;
> +}
> +
> /**
> * register_netdevice - register a network device
> * @dev: device to register
> @@ -5001,24 +5029,10 @@ int register_netdevice(struct net_device *dev)
>
> dev->iflink = -1;
>
> -#ifdef CONFIG_RPS
> - if (!dev->num_rx_queues) {
> - /*
> - * Allocate a single RX queue if driver never called
> - * alloc_netdev_mq
> - */
> -
> - dev->_rx = kzalloc(sizeof(struct netdev_rx_queue), GFP_KERNEL);
> - if (!dev->_rx) {
> - ret = -ENOMEM;
> - goto out;
> - }
> + ret = netif_alloc_rx_queues(dev);
> + if (ret)
> + goto out;
>
> - dev->_rx->first = dev->_rx;
> - atomic_set(&dev->_rx->count, 1);
> - dev->num_rx_queues = 1;
> - }
> -#endif
> /* Init, if this function is available */
> if (dev->netdev_ops->ndo_init) {
> ret = dev->netdev_ops->ndo_init(dev);
> @@ -5414,10 +5428,6 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
> struct net_device *dev;
> size_t alloc_size;
> struct net_device *p;
> -#ifdef CONFIG_RPS
> - struct netdev_rx_queue *rx;
> - int i;
> -#endif
>
> BUG_ON(strlen(name) >= sizeof(dev->name));
>
> @@ -5443,29 +5453,12 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
> goto free_p;
> }
>
> -#ifdef CONFIG_RPS
> - rx = kcalloc(queue_count, sizeof(struct netdev_rx_queue), GFP_KERNEL);
> - if (!rx) {
> - printk(KERN_ERR "alloc_netdev: Unable to allocate "
> - "rx queues.\n");
> - goto free_tx;
> - }
> -
> - atomic_set(&rx->count, queue_count);
> -
> - /*
> - * Set a pointer to first element in the array which holds the
> - * reference count.
> - */
> - for (i = 0; i < queue_count; i++)
> - rx[i].first = rx;
> -#endif
>
> dev = PTR_ALIGN(p, NETDEV_ALIGN);
> dev->padded = (char *)dev - (char *)p;
>
> if (dev_addr_init(dev))
> - goto free_rx;
> + goto free_tx;
>
> dev_mc_init(dev);
> dev_uc_init(dev);
> @@ -5477,7 +5470,6 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
> dev->real_num_tx_queues = queue_count;
>
> #ifdef CONFIG_RPS
> - dev->_rx = rx;
> dev->num_rx_queues = queue_count;
> #endif
>
> @@ -5495,11 +5487,7 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
> strcpy(dev->name, name);
> return dev;
>
> -free_rx:
> -#ifdef CONFIG_RPS
> - kfree(rx);
> free_tx:
> -#endif
> kfree(tx);
> free_p:
> kfree(p);
>
--
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