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Date: Wed, 22 Feb 2017 11:38:54 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: netdev@...r.kernel.org
Cc: Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH RFC v2 05/12] sock: sendmsg zerocopy notification coalescing
From: Willem de Bruijn <willemb@...gle.com>
In the simple case, each sendmsg() call generates data and eventually
a zerocopy ready notification N, where N indicates the Nth successful
invocation of sendmsg() with the MSG_ZEROCOPY flag on this socket.
TCP and corked sockets can cause sendmsg() calls to append to a single
sk_buff and ubuf_info. Modify the notification path to return an
inclusive range of notifications [N..N+m].
Add skb_zerocopy_realloc() to reuse ubuf_info across sendmsg() calls
and modify the notification path to return a range.
For the case of reliable ordered transmission (TCP), only the upper
value of the range to be read, as the lower value is guaranteed to
be 1 above the last read notification.
Additionally, coalesce notifications in this common case: if an
skb_uarg [1, 1] is queued while [0, 0] is already on the queue,
just modify the head of the queue to read [0, 1].
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
---
include/linux/skbuff.h | 21 +++++++++++-
net/core/skbuff.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 107 insertions(+), 6 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c7b42272b409..eedac9fd3f0f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -406,13 +406,21 @@ enum {
struct ubuf_info {
void (*callback)(struct ubuf_info *, bool zerocopy_success);
void *ctx;
- unsigned long desc;
+ union {
+ unsigned long desc;
+ struct {
+ u32 id;
+ u16 len;
+ };
+ };
atomic_t refcnt;
};
#define skb_uarg(SKB) ((struct ubuf_info *)(skb_shinfo(SKB)->destructor_arg))
struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size);
+struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, size_t size,
+ struct ubuf_info *uarg);
static inline void sock_zerocopy_get(struct ubuf_info *uarg)
{
@@ -420,6 +428,7 @@ static inline void sock_zerocopy_get(struct ubuf_info *uarg)
}
void sock_zerocopy_put(struct ubuf_info *uarg);
+void sock_zerocopy_put_abort(struct ubuf_info *uarg);
void sock_zerocopy_callback(struct ubuf_info *uarg, bool success);
@@ -1276,6 +1285,16 @@ static inline void skb_zcopy_clear(struct sk_buff *skb)
}
}
+static inline void skb_zcopy_abort(struct sk_buff *skb)
+{
+ struct ubuf_info *uarg = skb_zcopy(skb);
+
+ if (uarg) {
+ sock_zerocopy_put_abort(uarg);
+ skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
+ }
+}
+
/**
* skb_queue_empty - check if a queue is empty
* @list: queue head
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index fcbdc91b2d24..7a1d6e7703a6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -928,7 +928,8 @@ struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size)
uarg = (void *)skb->cb;
uarg->callback = sock_zerocopy_callback;
- uarg->desc = atomic_inc_return(&sk->sk_zckey) - 1;
+ uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
+ uarg->len = 1;
atomic_set(&uarg->refcnt, 0);
sock_hold(sk);
@@ -941,24 +942,94 @@ static inline struct sk_buff *skb_from_uarg(struct ubuf_info *uarg)
return container_of((void *)uarg, struct sk_buff, cb);
}
+struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, size_t size,
+ struct ubuf_info *uarg)
+{
+ if (uarg) {
+ u32 next;
+
+ /* realloc only when socket is locked (TCP, UDP cork),
+ * so uarg->len and sk_zckey access is serialized
+ */
+ BUG_ON(!sock_owned_by_user(sk));
+
+ if (unlikely(uarg->len == USHRT_MAX - 1))
+ return NULL;
+
+ next = (u32)atomic_read(&sk->sk_zckey);
+ if ((u32)(uarg->id + uarg->len) == next) {
+ uarg->len++;
+ atomic_set(&sk->sk_zckey, ++next);
+ return uarg;
+ }
+ }
+
+ return sock_zerocopy_alloc(sk, size);
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_realloc);
+
+static bool skb_zerocopy_notify_extend(struct sk_buff *skb, u32 lo, u16 len)
+{
+ struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
+ s64 sum_len;
+ u32 old_lo, old_hi;
+
+ old_lo = serr->ee.ee_info;
+ old_hi = serr->ee.ee_data;
+ sum_len = old_hi - old_lo + 1 + len;
+ if (old_hi < old_lo)
+ sum_len += (1ULL << 32);
+
+ if (sum_len >= (1ULL << 32))
+ return false;
+
+ if (lo != old_hi + 1)
+ return false;
+
+ serr->ee.ee_data += len;
+ return true;
+}
+
void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
{
struct sock_exterr_skb *serr;
- struct sk_buff *skb = skb_from_uarg(uarg);
+ struct sk_buff *head, *skb = skb_from_uarg(uarg);
struct sock *sk = skb->sk;
- u16 id = uarg->desc;
+ struct sk_buff_head *q = &sk->sk_error_queue;
+ unsigned long flags;
+ u32 lo, hi;
+ u16 len;
+
+ /* if !len, there was only 1 call, and it was aborted
+ * so do not queue a completion notification
+ */
+ if (!uarg->len)
+ goto free;
+
+ len = uarg->len;
+ lo = uarg->id;
+ hi = uarg->id + len - 1;
serr = SKB_EXT_ERR(skb);
memset(serr, 0, sizeof(*serr));
serr->ee.ee_errno = 0;
serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
- serr->ee.ee_data = id;
+ serr->ee.ee_data = hi;
+ serr->ee.ee_info = lo;
- skb_queue_tail(&sk->sk_error_queue, skb);
+ spin_lock_irqsave(&q->lock, flags);
+ head = skb_peek(q);
+ if (!head || !skb_zerocopy_notify_extend(head, lo, len)) {
+ __skb_queue_tail(q, skb);
+ skb = NULL;
+ }
+ spin_unlock_irqrestore(&q->lock, flags);
if (!sock_flag(sk, SOCK_DEAD))
sk->sk_error_report(sk);
+free:
+ consume_skb(skb);
sock_put(sk);
}
EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
@@ -974,6 +1045,17 @@ void sock_zerocopy_put(struct ubuf_info *uarg)
}
EXPORT_SYMBOL_GPL(sock_zerocopy_put);
+/* only called when sendmsg returns with error; no notification for this call */
+void sock_zerocopy_put_abort(struct ubuf_info *uarg)
+{
+ if (uarg) {
+ uarg->len--;
+ atomic_dec(&skb_from_uarg(uarg)->sk->sk_zckey);
+ sock_zerocopy_put(uarg);
+ }
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_put_abort);
+
bool skb_zerocopy_alloc(struct sk_buff *skb, size_t size)
{
struct ubuf_info *uarg;
--
2.11.0.483.g087da7b7c-goog
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