From 044304181fbeac4c1c90ae56f7908170d2f66098 Mon Sep 17 00:00:00 2001 From: Dust Li Date: Tue, 1 Mar 2022 17:44:00 +0800 Subject: [PATCH] net/smc: correct settings of RMB window update limit BugLink: https://bugs.launchpad.net/bugs/1969107 [ 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 Signed-off-by: David S. Miller Signed-off-by: Sasha Levin (cherry picked from commit 58758110912d244f9acb80a3e6ffe1dd9c4d9070) Signed-off-by: Paolo Pisati --- 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 7872717d53da..79afef85f7cf 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1899,7 +1899,7 @@ 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 */ -- 2.39.2