On Wed, 2013-06-19 at 13:40 +0800, Jason Wang wrote:
> Currently, we use kcalloc to allocate rx/tx queues for a net device which
> could
> be easily lead to a high order memory allocation request when initializing a
> multiqueue net device. We can simply avoid this by switching to use flex array
> which always allocate at order zero.
>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> include/linux/netdevice.h | 13 ++++++----
> net/core/dev.c | 57 ++++++++++++++++++++++++++++++++------------
> net/core/net-sysfs.c | 15 +++++++----
> 3 files changed, 58 insertions(+), 27 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 09b4188..c0b5d04 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -32,6 +32,7 @@
> #include <linux/atomic.h>
> #include <asm/cache.h>
> #include <asm/byteorder.h>
> +#include <linux/flex_array.h>
>
> #include <linux/percpu.h>
> #include <linux/rculist.h>
> @@ -1230,7 +1231,7 @@ struct net_device {
>
>
> #ifdef CONFIG_RPS
> - struct netdev_rx_queue *_rx;
> + struct flex_array *_rx;
>
> /* Number of RX queues allocated at register_netdev() time */
> unsigned int num_rx_queues;
> @@ -1250,7 +1251,7 @@ struct net_device {
> /*
> * Cache lines mostly used on transmit path
> */
> - struct netdev_queue *_tx ____cacheline_aligned_in_smp;
> + struct flex_array *_tx ____cacheline_aligned_in_smp;
>
Using flex_array and adding overhead in this super critical part of
network stack, only to avoid order-1 allocations done in GFP_KERNEL
context is simply insane.
We can revisit this in 2050 if we ever need order-4 allocations or so,
and still use 4K pages.
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