xsk: Consolidate to one single cached producer pointer
Currently, the xsk ring code has two cached producer pointers: prod_head and prod_tail. This patch consolidates these two into a single one called cached_prod to make the code simpler and easier to maintain. This will be in line with the user space part of the the code found in libbpf, that only uses a single cached pointer. The Rx path only uses the two top level functions xskq_produce_batch_desc and xskq_produce_flush_desc and they both use prod_head and never prod_tail. So just move them over to cached_prod. The Tx XDP_DRV path uses xskq_produce_addr_lazy and xskq_produce_flush_addr_n and unnecessarily operates on both prod_tail and prod_head, so move them over to just use cached_prod by skipping the intermediate step of updating prod_tail. The Tx path in XDP_SKB mode uses xskq_reserve_addr and xskq_produce_addr. They currently use both cached pointers, but we can operate on the global producer pointer in xskq_produce_addr since it has to be updated anyway, thus eliminating the use of both cached pointers. We can also remove the xskq_nb_free in xskq_produce_addr since it is already called in xskq_reserve_addr. No need to do it twice. When there is only one cached producer pointer, we can also simplify xskq_nb_free by removing one argument. Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/1576759171-28550-4-git-send-email-magnus.karlsson@intel.com
This commit is contained in:
parent
11cc2d2149
commit
d7012f05e3
|
@ -35,8 +35,7 @@ struct xsk_queue {
|
|||
u64 size;
|
||||
u32 ring_mask;
|
||||
u32 nentries;
|
||||
u32 prod_head;
|
||||
u32 prod_tail;
|
||||
u32 cached_prod;
|
||||
u32 cons_head;
|
||||
u32 cons_tail;
|
||||
struct xdp_ring *ring;
|
||||
|
@ -94,39 +93,39 @@ static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
|
|||
|
||||
static inline u32 xskq_nb_avail(struct xsk_queue *q, u32 dcnt)
|
||||
{
|
||||
u32 entries = q->prod_tail - q->cons_tail;
|
||||
u32 entries = q->cached_prod - q->cons_tail;
|
||||
|
||||
if (entries == 0) {
|
||||
/* Refresh the local pointer */
|
||||
q->prod_tail = READ_ONCE(q->ring->producer);
|
||||
entries = q->prod_tail - q->cons_tail;
|
||||
q->cached_prod = READ_ONCE(q->ring->producer);
|
||||
entries = q->cached_prod - q->cons_tail;
|
||||
}
|
||||
|
||||
return (entries > dcnt) ? dcnt : entries;
|
||||
}
|
||||
|
||||
static inline u32 xskq_nb_free(struct xsk_queue *q, u32 producer, u32 dcnt)
|
||||
static inline u32 xskq_nb_free(struct xsk_queue *q, u32 dcnt)
|
||||
{
|
||||
u32 free_entries = q->nentries - (producer - q->cons_tail);
|
||||
u32 free_entries = q->nentries - (q->cached_prod - q->cons_tail);
|
||||
|
||||
if (free_entries >= dcnt)
|
||||
return free_entries;
|
||||
|
||||
/* Refresh the local tail pointer */
|
||||
q->cons_tail = READ_ONCE(q->ring->consumer);
|
||||
return q->nentries - (producer - q->cons_tail);
|
||||
return q->nentries - (q->cached_prod - q->cons_tail);
|
||||
}
|
||||
|
||||
static inline bool xskq_has_addrs(struct xsk_queue *q, u32 cnt)
|
||||
{
|
||||
u32 entries = q->prod_tail - q->cons_tail;
|
||||
u32 entries = q->cached_prod - q->cons_tail;
|
||||
|
||||
if (entries >= cnt)
|
||||
return true;
|
||||
|
||||
/* Refresh the local pointer. */
|
||||
q->prod_tail = READ_ONCE(q->ring->producer);
|
||||
entries = q->prod_tail - q->cons_tail;
|
||||
q->cached_prod = READ_ONCE(q->ring->producer);
|
||||
entries = q->cached_prod - q->cons_tail;
|
||||
|
||||
return entries >= cnt;
|
||||
}
|
||||
|
@ -220,17 +219,15 @@ static inline void xskq_discard_addr(struct xsk_queue *q)
|
|||
static inline int xskq_produce_addr(struct xsk_queue *q, u64 addr)
|
||||
{
|
||||
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
|
||||
|
||||
if (xskq_nb_free(q, q->prod_tail, 1) == 0)
|
||||
return -ENOSPC;
|
||||
unsigned int idx = q->ring->producer;
|
||||
|
||||
/* A, matches D */
|
||||
ring->desc[q->prod_tail++ & q->ring_mask] = addr;
|
||||
ring->desc[idx++ & q->ring_mask] = addr;
|
||||
|
||||
/* Order producer and data */
|
||||
smp_wmb(); /* B, matches C */
|
||||
|
||||
WRITE_ONCE(q->ring->producer, q->prod_tail);
|
||||
WRITE_ONCE(q->ring->producer, idx);
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
@ -238,11 +235,11 @@ static inline int xskq_produce_addr_lazy(struct xsk_queue *q, u64 addr)
|
|||
{
|
||||
struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
|
||||
|
||||
if (xskq_nb_free(q, q->prod_head, 1) == 0)
|
||||
if (xskq_nb_free(q, 1) == 0)
|
||||
return -ENOSPC;
|
||||
|
||||
/* A, matches D */
|
||||
ring->desc[q->prod_head++ & q->ring_mask] = addr;
|
||||
ring->desc[q->cached_prod++ & q->ring_mask] = addr;
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
@ -252,17 +249,16 @@ static inline void xskq_produce_flush_addr_n(struct xsk_queue *q,
|
|||
/* Order producer and data */
|
||||
smp_wmb(); /* B, matches C */
|
||||
|
||||
q->prod_tail += nb_entries;
|
||||
WRITE_ONCE(q->ring->producer, q->prod_tail);
|
||||
WRITE_ONCE(q->ring->producer, q->ring->producer + nb_entries);
|
||||
}
|
||||
|
||||
static inline int xskq_reserve_addr(struct xsk_queue *q)
|
||||
{
|
||||
if (xskq_nb_free(q, q->prod_head, 1) == 0)
|
||||
if (xskq_nb_free(q, 1) == 0)
|
||||
return -ENOSPC;
|
||||
|
||||
/* A, matches D */
|
||||
q->prod_head++;
|
||||
q->cached_prod++;
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
@ -340,11 +336,11 @@ static inline int xskq_produce_batch_desc(struct xsk_queue *q,
|
|||
struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
|
||||
unsigned int idx;
|
||||
|
||||
if (xskq_nb_free(q, q->prod_head, 1) == 0)
|
||||
if (xskq_nb_free(q, 1) == 0)
|
||||
return -ENOSPC;
|
||||
|
||||
/* A, matches D */
|
||||
idx = (q->prod_head++) & q->ring_mask;
|
||||
idx = q->cached_prod++ & q->ring_mask;
|
||||
ring->desc[idx].addr = addr;
|
||||
ring->desc[idx].len = len;
|
||||
|
||||
|
@ -356,8 +352,7 @@ static inline void xskq_produce_flush_desc(struct xsk_queue *q)
|
|||
/* Order producer and data */
|
||||
smp_wmb(); /* B, matches C */
|
||||
|
||||
q->prod_tail = q->prod_head;
|
||||
WRITE_ONCE(q->ring->producer, q->prod_tail);
|
||||
WRITE_ONCE(q->ring->producer, q->cached_prod);
|
||||
}
|
||||
|
||||
static inline bool xskq_full_desc(struct xsk_queue *q)
|
||||
|
|
Loading…
Reference in a new issue