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authorMagnus Karlsson <magnus.karlsson@intel.com>2019-12-19 13:39:22 +0100
committerAlexei Starovoitov <ast@kernel.org>2019-12-20 16:00:09 -0800
commitd7012f05e3ca5aba92770c370895092d4882e8c2 (patch)
tree864e1def2e5a94e91cd47aa58ac4672223fa3683 /net
parent11cc2d21499cabe7e7964389634ed1de3ee91d33 (diff)
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
Diffstat (limited to 'net')
-rw-r--r--net/xdp/xsk_queue.h47
1 files changed, 21 insertions, 26 deletions
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index b28f9da7b317..7ad80748f209 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -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)