* [PATCH] v3.19.8: tcp: re-enable high throughput for low pacing rate
@ 2019-05-28 18:34 Sergej Benilov
2019-05-28 18:42 ` Eric Dumazet
0 siblings, 1 reply; 2+ messages in thread
From: Sergej Benilov @ 2019-05-28 18:34 UTC (permalink / raw)
To: davem, kuznet, yoshfuji, netdev; +Cc: Sergej Benilov
Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing",
the TSQ limit is computed as the smaller of
sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10).
For low pacing rates, this approach sets a low limit, reducing throughput dramatically.
Compute the limit as the greater of sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10).
Test:
netperf -H remote -l -2000000 -- -s 1000000
before patch:
MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
87380 327680 327680 250.17 0.06
after patch:
MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
87380 327680 327680 1.29 12.54
Signed-off-by: Sergej Benilov <sergej.benilov@googlemail.com>
---
net/ipv4/tcp_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e625be56..71efca72 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2054,7 +2054,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
* One example is wifi aggregation (802.11 AMPDU)
*/
limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
- limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
+ limit = max_t(u32, limit, sysctl_tcp_limit_output_bytes);
if (atomic_read(&sk->sk_wmem_alloc) > limit) {
set_bit(TSQ_THROTTLED, &tp->tsq_flags);
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] v3.19.8: tcp: re-enable high throughput for low pacing rate
2019-05-28 18:34 [PATCH] v3.19.8: tcp: re-enable high throughput for low pacing rate Sergej Benilov
@ 2019-05-28 18:42 ` Eric Dumazet
0 siblings, 0 replies; 2+ messages in thread
From: Eric Dumazet @ 2019-05-28 18:42 UTC (permalink / raw)
To: Sergej Benilov, davem, kuznet, yoshfuji, netdev
On 5/28/19 11:34 AM, Sergej Benilov wrote:
> Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing",
> the TSQ limit is computed as the smaller of
> sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10).
> For low pacing rates, this approach sets a low limit, reducing throughput dramatically.
...
>
> Signed-off-by: Sergej Benilov <sergej.benilov@googlemail.com>
> ---
> net/ipv4/tcp_output.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index e625be56..71efca72 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2054,7 +2054,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
> * One example is wifi aggregation (802.11 AMPDU)
> */
> limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
> - limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
> + limit = max_t(u32, limit, sysctl_tcp_limit_output_bytes);
>
> if (atomic_read(&sk->sk_wmem_alloc) > limit) {
> set_bit(TSQ_THROTTLED, &tp->tsq_flags);
>
NACK again, for the same reasons.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-05-28 18:42 ` Eric Dumazet
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