From: Arjun Roy arjunroy@google.com
stable inclusion form stable-v5.10.82 commit 5f7aadf03f98d641b32837f32a401e543d6e5a69 bugzilla: 185877 https://gitee.com/openeuler/kernel/issues/I4QU6V
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 18fb76ed53865c1b5d5f0157b1b825704590beb5 ]
When TCP receive zerocopy does not successfully map the entire requested space, it outputs a 'hint' that the caller should recvmsg().
Augment zerocopy to accept a user buffer that it tries to copy this hint into - if it is possible to copy the entire hint, it will do so. This elides a recvmsg() call for received traffic that isn't exactly page-aligned in size.
This was tested with RPC-style traffic of arbitrary sizes. Normally, each received message required at least one getsockopt() call, and one recvmsg() call for the remaining unaligned data.
With this change, almost all of the recvmsg() calls are eliminated, leading to a savings of about 25%-50% in number of system calls for RPC-style workloads.
Signed-off-by: Arjun Roy arjunroy@google.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: Soheil Hassas Yeganeh soheil@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- include/uapi/linux/tcp.h | 2 + net/ipv4/tcp.c | 84 ++++++++++++++++++++++++++++++++-------- 2 files changed, 70 insertions(+), 16 deletions(-)
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index cfcb10b75483..62db78b9c1a0 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -349,5 +349,7 @@ struct tcp_zerocopy_receive { __u32 recv_skip_hint; /* out: amount of bytes to skip */ __u32 inq; /* out: amount of bytes in read queue */ __s32 err; /* out: socket error */ + __u64 copybuf_address; /* in: copybuf address (small reads) */ + __s32 copybuf_len; /* in/out: copybuf bytes avail/used or error */ }; #endif /* _UAPI_LINUX_TCP_H */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 1d6efb6c6542..3305574256fd 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1750,6 +1750,52 @@ int tcp_mmap(struct file *file, struct socket *sock, } EXPORT_SYMBOL(tcp_mmap);
+static int tcp_copy_straggler_data(struct tcp_zerocopy_receive *zc, + struct sk_buff *skb, u32 copylen, + u32 *offset, u32 *seq) +{ + unsigned long copy_address = (unsigned long)zc->copybuf_address; + struct msghdr msg = {}; + struct iovec iov; + int err; + + if (copy_address != zc->copybuf_address) + return -EINVAL; + + err = import_single_range(READ, (void __user *)copy_address, + copylen, &iov, &msg.msg_iter); + if (err) + return err; + err = skb_copy_datagram_msg(skb, *offset, &msg, copylen); + if (err) + return err; + zc->recv_skip_hint -= copylen; + *offset += copylen; + *seq += copylen; + return (__s32)copylen; +} + +static int tcp_zerocopy_handle_leftover_data(struct tcp_zerocopy_receive *zc, + struct sock *sk, + struct sk_buff *skb, + u32 *seq, + s32 copybuf_len) +{ + u32 offset, copylen = min_t(u32, copybuf_len, zc->recv_skip_hint); + + if (!copylen) + return 0; + /* skb is null if inq < PAGE_SIZE. */ + if (skb) + offset = *seq - TCP_SKB_CB(skb)->seq; + else + skb = tcp_recv_skb(sk, *seq, &offset); + + zc->copybuf_len = tcp_copy_straggler_data(zc, skb, copylen, &offset, + seq); + return zc->copybuf_len < 0 ? 0 : copylen; +} + static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma, struct page **pages, unsigned long pages_to_map, @@ -1783,8 +1829,10 @@ static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma, static int tcp_zerocopy_receive(struct sock *sk, struct tcp_zerocopy_receive *zc) { + u32 length = 0, offset, vma_len, avail_len, aligned_len, copylen = 0; unsigned long address = (unsigned long)zc->address; - u32 length = 0, seq, offset, zap_len; + s32 copybuf_len = zc->copybuf_len; + struct tcp_sock *tp = tcp_sk(sk); #define PAGE_BATCH_SIZE 8 struct page *pages[PAGE_BATCH_SIZE]; const skb_frag_t *frags = NULL; @@ -1792,10 +1840,12 @@ static int tcp_zerocopy_receive(struct sock *sk, struct sk_buff *skb = NULL; unsigned long pg_idx = 0; unsigned long curr_addr; - struct tcp_sock *tp; - int inq; + u32 seq = tp->copied_seq; + int inq = tcp_inq(sk); int ret;
+ zc->copybuf_len = 0; + if (address & (PAGE_SIZE - 1) || address != zc->address) return -EINVAL;
@@ -1804,8 +1854,6 @@ static int tcp_zerocopy_receive(struct sock *sk,
sock_rps_record_flow(sk);
- tp = tcp_sk(sk); - mmap_read_lock(current->mm);
vma = find_vma(current->mm, address); @@ -1813,17 +1861,16 @@ static int tcp_zerocopy_receive(struct sock *sk, mmap_read_unlock(current->mm); return -EINVAL; } - zc->length = min_t(unsigned long, zc->length, vma->vm_end - address); - - seq = tp->copied_seq; - inq = tcp_inq(sk); - zc->length = min_t(u32, zc->length, inq); - zap_len = zc->length & ~(PAGE_SIZE - 1); - if (zap_len) { - zap_page_range(vma, address, zap_len); + vma_len = min_t(unsigned long, zc->length, vma->vm_end - address); + avail_len = min_t(u32, vma_len, inq); + aligned_len = avail_len & ~(PAGE_SIZE - 1); + if (aligned_len) { + zap_page_range(vma, address, aligned_len); + zc->length = aligned_len; zc->recv_skip_hint = 0; } else { - zc->recv_skip_hint = zc->length; + zc->length = avail_len; + zc->recv_skip_hint = avail_len; } ret = 0; curr_addr = address; @@ -1892,13 +1939,18 @@ static int tcp_zerocopy_receive(struct sock *sk, } out: mmap_read_unlock(current->mm); - if (length) { + /* Try to copy straggler data. */ + if (!ret) + copylen = tcp_zerocopy_handle_leftover_data(zc, sk, skb, &seq, + copybuf_len); + + if (length + copylen) { WRITE_ONCE(tp->copied_seq, seq); tcp_rcv_space_adjust(sk);
/* Clean up data we have read: This will do ACK frames. */ tcp_recv_skb(sk, seq, &offset); - tcp_cleanup_rbuf(sk, length); + tcp_cleanup_rbuf(sk, length + copylen); ret = 0; if (length == zc->length) zc->recv_skip_hint = 0;