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xen-netback: refactor guest rx

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Refactor the to-guest (rx) path to:

1. Push responses for completed skbs earlier, reducing latency.

2. Reduce the per-queue memory overhead by greatly reducing the
   maximum number of grant copy ops in each hypercall (from 4352 to
   64).  Each struct xenvif_queue is now only 44 kB instead of 220 kB.

3. Make the code more maintainable.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
[re-based]
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Vrabel
2016-10-04 10:29:14 +01:00
committed by David S. Miller
parent fedbc8c132
commit eb1723a29b
2 changed files with 254 additions and 423 deletions
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23
drivers/net/xen-netback/common.h
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@@ -91,13 +91,6 @@ struct xenvif_rx_meta {
*/
#define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)
/* It's possible for an skb to have a maximal number of frags
* but still be less than MAX_BUFFER_OFFSET in size. Thus the
* worst-case number of copy operations is MAX_XEN_SKB_FRAGS per
* ring slot.
*/
#define MAX_GRANT_COPY_OPS (MAX_XEN_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)
#define NETBACK_INVALID_HANDLE -1
/* To avoid confusion, we define XEN_NETBK_LEGACY_SLOTS_MAX indicating
@@ -133,6 +126,14 @@ struct xenvif_stats {
unsigned long tx_frag_overflow;
};
#define COPY_BATCH_SIZE 64
struct xenvif_copy_state {
struct gnttab_copy op[COPY_BATCH_SIZE];
RING_IDX idx[COPY_BATCH_SIZE];
unsigned int num;
};
struct xenvif_queue { /* Per-queue data for xenvif */
unsigned int id; /* Queue ID, 0-based */
char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
@@ -189,12 +190,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
unsigned long last_rx_time;
bool stalled;
struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];
/* We create one meta structure per ring request we consume, so
* the maximum number is the same as the ring size.
*/
struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE];
struct xenvif_copy_state rx_copy;
/* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */
unsigned long credit_bytes;
@@ -358,6 +354,7 @@ int xenvif_dealloc_kthread(void *data);
irqreturn_t xenvif_ctrl_irq_fn(int irq, void *data);
void xenvif_rx_action(struct xenvif_queue *queue);
void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);
void xenvif_carrier_on(struct xenvif *vif);