Re: [RFC 1/4] net: allow large number of rx queues

Sergei Shtylyov
2014-08-18T17:43:46Z

Hello.

On 08/18/2014 05:37 PM, Pankaj Gupta wrote:

> netif_alloc_rx_queues() uses kcalloc() to allocate memory
> for "struct netdev_queue *_rx" array.
> If we are doing large rx queue allocation kcalloc() might
> fail, so this patch does a fallback to vzalloc().
> Similar implementation is done for tx queue allocation in
> netif_alloc_netdev_queues().

> We avoid failure of high order memory allocation
> with the help of vzalloc(), this allows us to do large
> rx and tx queue allocation which in turn helps us to
> increase the number of queues in tun.

> As vmalloc() adds overhead on a critical network path,
> __GFP_REPEAT flag is used with kzalloc() to do this fallback
> only when really needed.

> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: David Gibson <dgibson@redhat.com>
> ---
> net/core/dev.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)

> diff --git a/net/core/dev.c b/net/core/dev.c
> index 1c15b18..a455a02 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5942,17 +5942,24 @@ void netif_stacked_transfer_operstate(const struct net_device *rootdev,
> EXPORT_SYMBOL(netif_stacked_transfer_operstate);
>
> #ifdef CONFIG_SYSFS
> +static void netif_free_rx_queues(struct net_device *dev)
> +{
> + kvfree(dev->_rx);
> +}
> +
> static int netif_alloc_rx_queues(struct net_device *dev)
> {
> unsigned int i, count = dev->num_rx_queues;
> struct netdev_rx_queue *rx;
> -
> + size_t sz = count * sizeof(*rx);

Please keep an empty line after declarations.

> BUG_ON(count < 1);
>

WBR, Sergei