From: Dust Li <dust.li@linux.alibaba.com>
Date: Tue, 1 Mar 2022 17:44:00 +0800
Subject: net/smc: correct settings of RMB window update limit
Patch-mainline: v5.18-rc1
Git-commit: 6bf536eb5c8ca011d1ff57b5c5f7c57ceac06a37
References: jsc#PED-612
rmbe_update_limit is used to limit announcing receive
window updating too frequently. RFC7609 request a minimal
increase in the window size of 10% of the receive buffer
space. But current implementation used:
min_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2)
and SOCK_MIN_SNDBUF / 2 == 2304 Bytes, which is almost
always less then 10% of the receive buffer space.
This causes the receiver always sending CDC message to
update its consumer cursor when it consumes more then 2K
of data. And as a result, we may encounter something like
"TCP silly window syndrome" when sending 2.5~8K message.
This patch fixes this using max(rmbe_size / 10, SOCK_MIN_SNDBUF / 2).
With this patch and SMC autocorking enabled, qperf 2K/4K/8K
tcp_bw test shows 45%/75%/40% increase in throughput respectively.
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
net/smc/smc_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1989,7 +1989,7 @@ static struct smc_buf_desc *smc_buf_get_
*/
static inline int smc_rmb_wnd_update_limit(int rmbe_size)
{
- return min_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2);
+ return max_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2);
}
/* map an rmb buf to a link */