From 6511882cdd82d6cf2178932fa9b78647d130b860 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Tue, 26 Oct 2021 16:29:15 -0700 Subject: mptcp: allocate fwd memory separately on the rx and tx path All the mptcp receive path is protected by the msk socket spinlock. As consequences, the tx path has to play a few tricks to allocate the forward memory without acquiring the spinlock multiple times, making the overall TX path quite complex. This patch tries to clean-up a bit the tx path, using completely separated fwd memory allocation, for the rx and the tx path. The forward memory allocated in the rx path is now accounted in msk->rmem_fwd_alloc and is (still) protected by the msk socket spinlock. To cope with the above we provide a few MPTCP-specific variants for the helpers to charge, uncharge, reclaim and free the forward memory in the receive path. msk->sk_forward_alloc now accounts only the forward memory for the tx path, we can use the plain core sock helper to manipulate it and drop quite a bit of complexity. On memory pressure, both rx and tx fwd memories are reclaimed. Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski --- net/mptcp/protocol.c | 225 +++++++++++++++++++++------------------------------ 1 file changed, 94 insertions(+), 131 deletions(-) (limited to 'net/mptcp/protocol.c') diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index cd6b11c9b54d..81ef592113a5 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -126,6 +126,11 @@ static void mptcp_drop(struct sock *sk, struct sk_buff *skb) __kfree_skb(skb); } +static void mptcp_rmem_charge(struct sock *sk, int size) +{ + mptcp_sk(sk)->rmem_fwd_alloc -= size; +} + static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, struct sk_buff *from) { @@ -142,7 +147,7 @@ static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq; kfree_skb_partial(from, fragstolen); atomic_add(delta, &sk->sk_rmem_alloc); - sk_mem_charge(sk, delta); + mptcp_rmem_charge(sk, delta); return true; } @@ -155,6 +160,44 @@ static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to, return mptcp_try_coalesce((struct sock *)msk, to, from); } +static void __mptcp_rmem_reclaim(struct sock *sk, int amount) +{ + amount >>= SK_MEM_QUANTUM_SHIFT; + mptcp_sk(sk)->rmem_fwd_alloc -= amount << SK_MEM_QUANTUM_SHIFT; + __sk_mem_reduce_allocated(sk, amount); +} + +static void mptcp_rmem_uncharge(struct sock *sk, int size) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + int reclaimable; + + msk->rmem_fwd_alloc += size; + reclaimable = msk->rmem_fwd_alloc - sk_unused_reserved_mem(sk); + + /* see sk_mem_uncharge() for the rationale behind the following schema */ + if (unlikely(reclaimable >= SK_RECLAIM_THRESHOLD)) + __mptcp_rmem_reclaim(sk, SK_RECLAIM_CHUNK); +} + +static void mptcp_rfree(struct sk_buff *skb) +{ + unsigned int len = skb->truesize; + struct sock *sk = skb->sk; + + atomic_sub(len, &sk->sk_rmem_alloc); + mptcp_rmem_uncharge(sk, len); +} + +static void mptcp_set_owner_r(struct sk_buff *skb, struct sock *sk) +{ + skb_orphan(skb); + skb->sk = sk; + skb->destructor = mptcp_rfree; + atomic_add(skb->truesize, &sk->sk_rmem_alloc); + mptcp_rmem_charge(sk, skb->truesize); +} + /* "inspired" by tcp_data_queue_ofo(), main differences: * - use mptcp seqs * - don't cope with sacks @@ -267,7 +310,29 @@ merge_right: end: skb_condense(skb); - skb_set_owner_r(skb, sk); + mptcp_set_owner_r(skb, sk); +} + +static bool mptcp_rmem_schedule(struct sock *sk, struct sock *ssk, int size) +{ + struct mptcp_sock *msk = mptcp_sk(sk); + int amt, amount; + + if (size < msk->rmem_fwd_alloc) + return true; + + amt = sk_mem_pages(size); + amount = amt << SK_MEM_QUANTUM_SHIFT; + msk->rmem_fwd_alloc += amount; + if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV)) { + if (ssk->sk_forward_alloc < amount) { + msk->rmem_fwd_alloc -= amount; + return false; + } + + ssk->sk_forward_alloc -= amount; + } + return true; } static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk, @@ -285,15 +350,8 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk, skb_orphan(skb); /* try to fetch required memory from subflow */ - if (!sk_rmem_schedule(sk, skb, skb->truesize)) { - int amount = sk_mem_pages(skb->truesize) << SK_MEM_QUANTUM_SHIFT; - - if (ssk->sk_forward_alloc < amount) - goto drop; - - ssk->sk_forward_alloc -= amount; - sk->sk_forward_alloc += amount; - } + if (!mptcp_rmem_schedule(sk, ssk, skb->truesize)) + goto drop; has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; @@ -313,7 +371,7 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk, if (tail && mptcp_try_coalesce(sk, tail, skb)) return true; - skb_set_owner_r(skb, sk); + mptcp_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); return true; } else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) { @@ -908,122 +966,20 @@ static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk, df->data_seq + df->data_len == msk->write_seq; } -static int mptcp_wmem_with_overhead(int size) -{ - return size + ((sizeof(struct mptcp_data_frag) * size) >> PAGE_SHIFT); -} - -static void __mptcp_wmem_reserve(struct sock *sk, int size) -{ - int amount = mptcp_wmem_with_overhead(size); - struct mptcp_sock *msk = mptcp_sk(sk); - - WARN_ON_ONCE(msk->wmem_reserved); - if (WARN_ON_ONCE(amount < 0)) - amount = 0; - - if (amount <= sk->sk_forward_alloc) - goto reserve; - - /* under memory pressure try to reserve at most a single page - * otherwise try to reserve the full estimate and fallback - * to a single page before entering the error path - */ - if ((tcp_under_memory_pressure(sk) && amount > PAGE_SIZE) || - !sk_wmem_schedule(sk, amount)) { - if (amount <= PAGE_SIZE) - goto nomem; - - amount = PAGE_SIZE; - if (!sk_wmem_schedule(sk, amount)) - goto nomem; - } - -reserve: - msk->wmem_reserved = amount; - sk->sk_forward_alloc -= amount; - return; - -nomem: - /* we will wait for memory on next allocation */ - msk->wmem_reserved = -1; -} - -static void __mptcp_update_wmem(struct sock *sk) +static void __mptcp_mem_reclaim_partial(struct sock *sk) { - struct mptcp_sock *msk = mptcp_sk(sk); + int reclaimable = mptcp_sk(sk)->rmem_fwd_alloc - sk_unused_reserved_mem(sk); lockdep_assert_held_once(&sk->sk_lock.slock); - if (!msk->wmem_reserved) - return; - - if (msk->wmem_reserved < 0) - msk->wmem_reserved = 0; - if (msk->wmem_reserved > 0) { - sk->sk_forward_alloc += msk->wmem_reserved; - msk->wmem_reserved = 0; - } -} - -static bool mptcp_wmem_alloc(struct sock *sk, int size) -{ - struct mptcp_sock *msk = mptcp_sk(sk); - - /* check for pre-existing error condition */ - if (msk->wmem_reserved < 0) - return false; - - if (msk->wmem_reserved >= size) - goto account; - - mptcp_data_lock(sk); - if (!sk_wmem_schedule(sk, size)) { - mptcp_data_unlock(sk); - return false; - } - - sk->sk_forward_alloc -= size; - msk->wmem_reserved += size; - mptcp_data_unlock(sk); - -account: - msk->wmem_reserved -= size; - return true; -} - -static void mptcp_wmem_uncharge(struct sock *sk, int size) -{ - struct mptcp_sock *msk = mptcp_sk(sk); - - if (msk->wmem_reserved < 0) - msk->wmem_reserved = 0; - msk->wmem_reserved += size; -} - -static void __mptcp_mem_reclaim_partial(struct sock *sk) -{ - lockdep_assert_held_once(&sk->sk_lock.slock); - __mptcp_update_wmem(sk); + __mptcp_rmem_reclaim(sk, reclaimable - 1); sk_mem_reclaim_partial(sk); } static void mptcp_mem_reclaim_partial(struct sock *sk) { - struct mptcp_sock *msk = mptcp_sk(sk); - - /* if we are experiencing a transint allocation error, - * the forward allocation memory has been already - * released - */ - if (msk->wmem_reserved < 0) - return; - mptcp_data_lock(sk); - sk->sk_forward_alloc += msk->wmem_reserved; - sk_mem_reclaim_partial(sk); - msk->wmem_reserved = sk->sk_forward_alloc; - sk->sk_forward_alloc = 0; + __mptcp_mem_reclaim_partial(sk); mptcp_data_unlock(sk); } @@ -1664,7 +1620,6 @@ out: /* __mptcp_alloc_tx_skb could have released some wmem and we are * not going to flush it via release_sock() */ - __mptcp_update_wmem(sk); if (copied) { tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle, info.size_goal); @@ -1701,7 +1656,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) /* silently ignore everything else */ msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL; - mptcp_lock_sock(sk, __mptcp_wmem_reserve(sk, min_t(size_t, 1 << 20, len))); + lock_sock(sk); timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); @@ -1749,17 +1704,17 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) psize = min_t(size_t, psize, msg_data_left(msg)); total_ts = psize + frag_truesize; - if (!mptcp_wmem_alloc(sk, total_ts)) + if (!sk_wmem_schedule(sk, total_ts)) goto wait_for_memory; if (copy_page_from_iter(dfrag->page, offset, psize, &msg->msg_iter) != psize) { - mptcp_wmem_uncharge(sk, psize + frag_truesize); ret = -EFAULT; goto out; } /* data successfully copied into the write queue */ + sk->sk_forward_alloc -= total_ts; copied += psize; dfrag->data_len += psize; frag_truesize += psize; @@ -1956,7 +1911,7 @@ static void __mptcp_update_rmem(struct sock *sk) return; atomic_sub(msk->rmem_released, &sk->sk_rmem_alloc); - sk_mem_uncharge(sk, msk->rmem_released); + mptcp_rmem_uncharge(sk, msk->rmem_released); WRITE_ONCE(msk->rmem_released, 0); } @@ -2024,7 +1979,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, if (unlikely(flags & MSG_ERRQUEUE)) return inet_recv_error(sk, msg, len, addr_len); - mptcp_lock_sock(sk, __mptcp_splice_receive_queue(sk)); + lock_sock(sk); if (unlikely(sk->sk_state == TCP_LISTEN)) { copied = -ENOTCONN; goto out_err; @@ -2504,7 +2459,7 @@ static int __mptcp_init_sock(struct sock *sk) __skb_queue_head_init(&msk->receive_queue); msk->out_of_order_queue = RB_ROOT; msk->first_pending = NULL; - msk->wmem_reserved = 0; + msk->rmem_fwd_alloc = 0; WRITE_ONCE(msk->rmem_released, 0); msk->timer_ival = TCP_RTO_MIN; @@ -2715,7 +2670,7 @@ static void __mptcp_destroy_sock(struct sock *sk) sk->sk_prot->destroy(sk); - WARN_ON_ONCE(msk->wmem_reserved); + WARN_ON_ONCE(msk->rmem_fwd_alloc); WARN_ON_ONCE(msk->rmem_released); sk_stream_kill_queues(sk); xfrm_sk_free_policy(sk); @@ -2948,8 +2903,14 @@ void mptcp_destroy_common(struct mptcp_sock *msk) /* move to sk_receive_queue, sk_stream_kill_queues will purge it */ skb_queue_splice_tail_init(&msk->receive_queue, &sk->sk_receive_queue); - + __skb_queue_purge(&sk->sk_receive_queue); skb_rbtree_purge(&msk->out_of_order_queue); + + /* move all the rx fwd alloc into the sk_mem_reclaim_final in + * inet_sock_destruct() will dispose it + */ + sk->sk_forward_alloc += msk->rmem_fwd_alloc; + msk->rmem_fwd_alloc = 0; mptcp_token_destroy(msk); mptcp_pm_free_anno_list(msk); } @@ -3031,10 +2992,6 @@ static void mptcp_release_cb(struct sock *sk) if (test_and_clear_bit(MPTCP_ERROR_REPORT, &mptcp_sk(sk)->flags)) __mptcp_error_report(sk); - /* push_pending may touch wmem_reserved, ensure we do the cleanup - * later - */ - __mptcp_update_wmem(sk); __mptcp_update_rmem(sk); } @@ -3184,6 +3141,11 @@ static void mptcp_shutdown(struct sock *sk, int how) __mptcp_wr_shutdown(sk); } +static int mptcp_forward_alloc_get(const struct sock *sk) +{ + return sk->sk_forward_alloc + mptcp_sk(sk)->rmem_fwd_alloc; +} + static struct proto mptcp_prot = { .name = "MPTCP", .owner = THIS_MODULE, @@ -3201,6 +3163,7 @@ static struct proto mptcp_prot = { .hash = mptcp_hash, .unhash = mptcp_unhash, .get_port = mptcp_get_port, + .forward_alloc_get = mptcp_forward_alloc_get, .sockets_allocated = &mptcp_sockets_allocated, .memory_allocated = &tcp_memory_allocated, .memory_pressure = &tcp_memory_pressure, -- cgit v1.2.3