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Message-Id: <20220418121217.940558387@linuxfoundation.org>
Date: Mon, 18 Apr 2022 14:13:20 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Dust Li <dust.li@...ux.alibaba.com>,
"David S. Miller" <davem@...emloft.net>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 219/284] net/smc: correct settings of RMB window update limit
From: Dust Li <dust.li@...ux.alibaba.com>
[ Upstream commit 6bf536eb5c8ca011d1ff57b5c5f7c57ceac06a37 ]
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@...ux.alibaba.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
net/smc/smc_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 7dc907a45c68..a28e06c70e52 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -499,7 +499,7 @@ struct smc_buf_desc *smc_buf_get_slot(struct smc_link_group *lgr,
*/
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);
}
static struct smc_buf_desc *smc_new_buf_create(struct smc_link_group *lgr,
--
2.35.1
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