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net: add gro_cells infrastructure

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This adds a new include file (include/net/gro_cells.h), to bring GRO
(Generic Receive Offload) capability to tunnels, in a modular way.

Because tunnels receive path is lockless, and GRO adds a serialization
using a napi_struct, I chose to add an array of up to
DEFAULT_MAX_NUM_RSS_QUEUES cells, so that multi queue devices wont be
slowed down because of GRO layer.

skb_get_rx_queue() is used as selector.

In the future, we might add optional fanout capabilities, using rxhash
for example.

With help from Ben Hutchings who reminded me
netif_get_num_default_rss_queues() function.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-09-27 19:29:05 +00:00 committed by David S. Miller
parent 861b650101
commit c9e6bc644e
2 changed files with 105 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

103
include/net/gro_cells.h Normal file
View file

@ -0,0 +1,103 @@
#ifndef _NET_GRO_CELLS_H
#define _NET_GRO_CELLS_H
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
struct gro_cell {
struct sk_buff_head napi_skbs;
struct napi_struct napi;
} ____cacheline_aligned_in_smp;
struct gro_cells {
unsigned int gro_cells_mask;
struct gro_cell *cells;
};
static inline void gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
{
unsigned long flags;
struct gro_cell *cell = gcells->cells;
struct net_device *dev = skb->dev;
if (!cell || skb_cloned(skb) || !(dev->features & NETIF_F_GRO)) {
netif_rx(skb);
return;
}
if (skb_rx_queue_recorded(skb))
cell += skb_get_rx_queue(skb) & gcells->gro_cells_mask;
if (skb_queue_len(&cell->napi_skbs) > netdev_max_backlog) {
atomic_long_inc(&dev->rx_dropped);
kfree_skb(skb);
return;
}
spin_lock_irqsave(&cell->napi_skbs.lock, flags);
__skb_queue_tail(&cell->napi_skbs, skb);
if (skb_queue_len(&cell->napi_skbs) == 1)
napi_schedule(&cell->napi);
spin_unlock_irqrestore(&cell->napi_skbs.lock, flags);
}
static inline int gro_cell_poll(struct napi_struct *napi, int budget)
{
struct gro_cell *cell = container_of(napi, struct gro_cell, napi);
struct sk_buff *skb;
int work_done = 0;
while (work_done < budget) {
skb = skb_dequeue(&cell->napi_skbs);
if (!skb)
break;
napi_gro_receive(napi, skb);
work_done++;
}
if (work_done < budget)
napi_complete(napi);
return work_done;
}
static inline int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
{
int i;
gcells->gro_cells_mask = roundup_pow_of_two(netif_get_num_default_rss_queues()) - 1;
gcells->cells = kcalloc(sizeof(struct gro_cell),
gcells->gro_cells_mask + 1,
GFP_KERNEL);
if (!gcells->cells)
return -ENOMEM;
for (i = 0; i <= gcells->gro_cells_mask; i++) {
struct gro_cell *cell = gcells->cells + i;
skb_queue_head_init(&cell->napi_skbs);
netif_napi_add(dev, &cell->napi, gro_cell_poll, 64);
napi_enable(&cell->napi);
}
return 0;
}
static inline void gro_cells_destroy(struct gro_cells *gcells)
{
struct gro_cell *cell = gcells->cells;
int i;
if (!cell)
return;
for (i = 0; i <= gcells->gro_cells_mask; i++,cell++) {
netif_napi_del(&cell->napi);
skb_queue_purge(&cell->napi_skbs);
}
kfree(gcells->cells);
gcells->cells = NULL;
}
#endif

2
net/core/dev.c
View file

@ -2645,6 +2645,8 @@ EXPORT_SYMBOL(dev_queue_xmit);
=======================================================================*/
int netdev_max_backlog __read_mostly = 1000;
EXPORT_SYMBOL(netdev_max_backlog);
int netdev_tstamp_prequeue __read_mostly = 1;
int netdev_budget __read_mostly = 300;
int weight_p __read_mostly = 64; /* old backlog weight */