From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTP id 8F1DA5A02E0 for ; Wed, 15 May 2024 17:34:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1715787272; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LEQodt1sHH1M4qYFGj/coQPVtLFI7PDvl1ePzxvQtgg=; b=GxpwAztHbsnzsNelcKvpROAzCBZc1VKQCqFdZ+Q9OuS6QalUjAYC3aWFjRoVzN5ez6Z4Oz dJ0TADK+Ei48eox/tocRwt347EQ3yYGfJb+J7m5oNjYY0eUgX2LObm1QGCPJjrIo5FiBuG ceqexnUfsLdkBSFC3WdK56GC8ocvxSc= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-112-vhLVP6xMMWGrCFmAw4wX8g-1; Wed, 15 May 2024 11:34:31 -0400 X-MC-Unique: vhLVP6xMMWGrCFmAw4wX8g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EFB2F8058CB for ; Wed, 15 May 2024 15:34:30 +0000 (UTC) Received: from fenrir.redhat.com (unknown [10.22.8.102]) by smtp.corp.redhat.com (Postfix) with ESMTP id 927273C27; Wed, 15 May 2024 15:34:30 +0000 (UTC) From: Jon Maloy To: passt-dev@passt.top, sbrivio@redhat.com, lvivier@redhat.com, dgibson@redhat.com, jmaloy@redhat.com Subject: [PATCH v4 2/3] tcp: leverage support of SO_PEEK_OFF socket option when available Date: Wed, 15 May 2024 11:34:28 -0400 Message-ID: <20240515153429.859185-3-jmaloy@redhat.com> In-Reply-To: <20240515153429.859185-1-jmaloy@redhat.com> References: <20240515153429.859185-1-jmaloy@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: Y3IN2XDQRLMBIBAACVQDAVGGVRF5HIKK X-Message-ID-Hash: Y3IN2XDQRLMBIBAACVQDAVGGVRF5HIKK X-MailFrom: jmaloy@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: >From linux-6.9.0 the kernel will contain commit 05ea491641d3 ("tcp: add support for SO_PEEK_OFF socket option"). This new feature makes is possible to call recv_msg(MSG_PEEK) and make it start reading data from a given offset set by the SO_PEEK_OFF socket option. This way, we can avoid repeated reading of already read bytes of a received message, hence saving read cycles when forwarding TCP messages in the host->name space direction. In this commit, we add functionality to leverage this feature when available, while we fall back to the previous behavior when not. Measurements with iperf3 shows that throughput increases with 15-20 percent in the host->namespace direction when this feature is used. Signed-off-by: Jon Maloy --- v2: - Some smaller changes as suggested by David Gibson and Stefano Brivio. - Moved initial set_peek_offset(0) to only the locations where the socket is set to ESTABLISHED. - Removed the per-packet synchronization between sk_peek_off and already_sent. Instead only doing it in retransmit situations. - The problem I found when trouble shooting the occasionally occurring out of synch values between 'already_sent' and 'sk_peek_offset' may have deeper implications that we may need to be investigate. v3: - Rebased to most recent version of tcp.c, plus the previous patch in this series. - Some changes based on feedback from PASST team v4: - Some small changes based on feedback from Stefan/David. --- tcp.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 50 insertions(+), 8 deletions(-) diff --git a/tcp.c b/tcp.c index 976dba8..4163bf9 100644 --- a/tcp.c +++ b/tcp.c @@ -511,6 +511,9 @@ static struct iovec tcp6_l2_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; static struct iovec tcp4_l2_flags_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; static struct iovec tcp6_l2_flags_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; +/* Does the kernel support TCP_PEEK_OFF? */ +static bool peek_offset_cap; + /* sendmsg() to socket */ static struct iovec tcp_iov [UIO_MAXIOV]; @@ -526,6 +529,20 @@ static_assert(ARRAY_SIZE(tc_hash) >= FLOW_MAX, int init_sock_pool4 [TCP_SOCK_POOL_SIZE]; int init_sock_pool6 [TCP_SOCK_POOL_SIZE]; +/** + * tcp_set_peek_offset() - Set SO_PEEK_OFF offset on a socket if supported + * @s: Socket to update + * @offset: Offset in bytes + */ +static void tcp_set_peek_offset(int s, int offset) +{ + if (!peek_offset_cap) + return; + + if (setsockopt(s, SOL_SOCKET, SO_PEEK_OFF, &offset, sizeof(offset))) + err("Failed to set SO_PEEK_OFF to %u in socket %i", offset, s); +} + /** * tcp_conn_epoll_events() - epoll events mask for given connection state * @events: Current connection events @@ -2197,14 +2214,15 @@ static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn) uint32_t already_sent, seq; struct iovec *iov; + /* How much have we read/sent since last received ack ? */ already_sent = conn->seq_to_tap - conn->seq_ack_from_tap; - if (SEQ_LT(already_sent, 0)) { /* RFC 761, section 2.1. */ flow_trace(conn, "ACK sequence gap: ACK for %u, sent: %u", conn->seq_ack_from_tap, conn->seq_to_tap); conn->seq_to_tap = conn->seq_ack_from_tap; already_sent = 0; + tcp_set_peek_offset(s, 0); } if (!wnd_scaled || already_sent >= wnd_scaled) { @@ -2222,11 +2240,16 @@ static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn) iov_rem = (wnd_scaled - already_sent) % mss; } - mh_sock.msg_iov = iov_sock; - mh_sock.msg_iovlen = fill_bufs + 1; - - iov_sock[0].iov_base = tcp_buf_discard; - iov_sock[0].iov_len = already_sent; + /* Prepare iov according to kernel capability */ + if (!peek_offset_cap) { + mh_sock.msg_iov = iov_sock; + iov_sock[0].iov_base = tcp_buf_discard; + iov_sock[0].iov_len = already_sent; + mh_sock.msg_iovlen = fill_bufs + 1; + } else { + mh_sock.msg_iov = &iov_sock[1]; + mh_sock.msg_iovlen = fill_bufs; + } if (( v4 && tcp4_payload_used + fill_bufs > TCP_FRAMES_MEM) || (!v4 && tcp6_payload_used + fill_bufs > TCP_FRAMES_MEM)) { @@ -2267,7 +2290,10 @@ static int tcp_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn) return 0; } - sendlen = len - already_sent; + sendlen = len; + if (!peek_offset_cap) + sendlen -= already_sent; + if (sendlen <= 0) { conn_flag(c, conn, STALLED); return 0; @@ -2438,6 +2464,7 @@ static int tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn, "fast re-transmit, ACK: %u, previous sequence: %u", max_ack_seq, conn->seq_to_tap); conn->seq_to_tap = max_ack_seq; + tcp_set_peek_offset(conn->sock, 0); tcp_data_from_sock(c, conn); } @@ -2530,6 +2557,7 @@ static void tcp_conn_from_sock_finish(struct ctx *c, struct tcp_tap_conn *conn, conn->seq_ack_to_tap = conn->seq_from_tap; conn_event(c, conn, ESTABLISHED); + tcp_set_peek_offset(conn->sock, 0); /* The client might have sent data already, which we didn't * dequeue waiting for SYN,ACK from tap -- check now. @@ -2610,6 +2638,7 @@ int tcp_tap_handler(struct ctx *c, uint8_t pif, sa_family_t af, goto reset; conn_event(c, conn, ESTABLISHED); + tcp_set_peek_offset(conn->sock, 0); if (th->fin) { conn->seq_from_tap++; @@ -2863,6 +2892,7 @@ void tcp_timer_handler(struct ctx *c, union epoll_ref ref) flow_dbg(conn, "ACK timeout, retry"); conn->retrans++; conn->seq_to_tap = conn->seq_ack_from_tap; + tcp_set_peek_offset(conn->sock, 0); tcp_data_from_sock(c, conn); tcp_timer_ctl(c, conn); } @@ -3154,7 +3184,8 @@ static void tcp_sock_refill_init(const struct ctx *c) */ int tcp_init(struct ctx *c) { - unsigned b; + unsigned int b, optv = 0; + int s; for (b = 0; b < TCP_HASH_TABLE_SIZE; b++) tc_hash[b] = FLOW_SIDX_NONE; @@ -3178,6 +3209,17 @@ int tcp_init(struct ctx *c) NS_CALL(tcp_ns_socks_init, c); } + /* Probe for SO_PEEK_OFF support */ + s = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, IPPROTO_TCP); + if (s < 0) { + warn("Temporary TCP socket creation failed"); + } else { + if (!setsockopt(s, SOL_SOCKET, SO_PEEK_OFF, &optv, sizeof(int))) + peek_offset_cap = true; + close(s); + } + info("SO_PEEK_OFF%ssupported", peek_offset_cap ? " " : " not "); + return 0; } -- 2.42.0