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Date: Fri, 1 Apr 2022 10:37:09 -0400 From: Sasha Levin <sashal@...nel.org> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org Cc: Dust Li <dust.li@...ux.alibaba.com>, "David S . Miller" <davem@...emloft.net>, Sasha Levin <sashal@...nel.org>, kgraul@...ux.ibm.com, kuba@...nel.org, pabeni@...hat.com, linux-s390@...r.kernel.org, netdev@...r.kernel.org Subject: [PATCH AUTOSEL 5.15 65/98] 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 dee336eef6d2..7401ec67ebcf 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1822,7 +1822,7 @@ 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 */ -- 2.34.1
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