| From d5d1f56850ca7750c61911c8bf657c7b8ff3b38e Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 1 Mar 2022 17:44:00 +0800 |
| Subject: net/smc: correct settings of RMB window update limit |
| |
| From: Dust Li <dust.li@linux.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@linux.alibaba.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Sasha Levin <sashal@kernel.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 d1cdc891c211..f1dc5b914771 100644 |
| --- a/net/smc/smc_core.c |
| +++ b/net/smc/smc_core.c |
| @@ -1904,7 +1904,7 @@ static struct smc_buf_desc *smc_buf_get_slot(int compressed_bufsize, |
| */ |
| 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 */ |
| -- |
| 2.35.1 |
| |