| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.17 116/343] net/smc: correct settings of RMB window update limit | Date | Tue, 12 Apr 2022 08:28:54 +0200 |
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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 be7d704976ff..f40f6ed0fbdb 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1989,7 +1989,7 @@ 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
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