diff options
| author | Eric Dumazet <edumazet@google.com> | 2013-08-27 05:46:32 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-11-04 04:30:59 -0800 |
| commit | 5e25ba5003ee5de0ba2be56bfd54d16d4b1b028d (patch) | |
| tree | 7a953aea4b06398a6f3c66835d6e76b8048acaa4 /include | |
| parent | 14e9c7db465387ede7f019c42f28c90f99fc2793 (diff) | |
tcp: TSO packets automatic sizing
[ Upstream commits 6d36824e730f247b602c90e8715a792003e3c5a7,
02cf4ebd82ff0ac7254b88e466820a290ed8289a, and parts of
7eec4174ff29cd42f2acfae8112f51c228545d40 ]
After hearing many people over past years complaining against TSO being
bursty or even buggy, we are proud to present automatic sizing of TSO
packets.
One part of the problem is that tcp_tso_should_defer() uses an heuristic
relying on upcoming ACKS instead of a timer, but more generally, having
big TSO packets makes little sense for low rates, as it tends to create
micro bursts on the network, and general consensus is to reduce the
buffering amount.
This patch introduces a per socket sk_pacing_rate, that approximates
the current sending rate, and allows us to size the TSO packets so
that we try to send one packet every ms.
This field could be set by other transports.
Patch has no impact for high speed flows, where having large TSO packets
makes sense to reach line rate.
For other flows, this helps better packet scheduling and ACK clocking.
This patch increases performance of TCP flows in lossy environments.
A new sysctl (tcp_min_tso_segs) is added, to specify the
minimal size of a TSO packet (default being 2).
A follow-up patch will provide a new packet scheduler (FQ), using
sk_pacing_rate as an input to perform optional per flow pacing.
This explains why we chose to set sk_pacing_rate to twice the current
rate, allowing 'slow start' ramp up.
sk_pacing_rate = 2 * cwnd * mss / srtt
v2: Neal Cardwell reported a suspect deferring of last two segments on
initial write of 10 MSS, I had to change tcp_tso_should_defer() to take
into account tp->xmit_size_goal_segs
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Van Jacobson <vanj@google.com>
Cc: Tom Herbert <therbert@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/sock.h | 2 | ||||
| -rw-r--r-- | include/net/tcp.h | 1 |
2 files changed, 3 insertions, 0 deletions
diff --git a/include/net/sock.h b/include/net/sock.h index 66772cf8c3c..cec4c723db9 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -230,6 +230,7 @@ struct cg_proto; * @sk_wmem_queued: persistent queue size * @sk_forward_alloc: space allocated forward * @sk_allocation: allocation mode + * @sk_pacing_rate: Pacing rate (if supported by transport/packet scheduler) * @sk_sndbuf: size of send buffer in bytes * @sk_flags: %SO_LINGER (l_onoff), %SO_BROADCAST, %SO_KEEPALIVE, * %SO_OOBINLINE settings, %SO_TIMESTAMPING settings @@ -355,6 +356,7 @@ struct sock { kmemcheck_bitfield_end(flags); int sk_wmem_queued; gfp_t sk_allocation; + u32 sk_pacing_rate; /* bytes per second */ netdev_features_t sk_route_caps; netdev_features_t sk_route_nocaps; int sk_gso_type; diff --git a/include/net/tcp.h b/include/net/tcp.h index 5bba80fbd1d..3fc77e90624 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -287,6 +287,7 @@ extern int sysctl_tcp_thin_dupack; extern int sysctl_tcp_early_retrans; extern int sysctl_tcp_limit_output_bytes; extern int sysctl_tcp_challenge_ack_limit; +extern int sysctl_tcp_min_tso_segs; extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; |