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@xxxxxxxxxxxxxxxxx>
---
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 29525d03b253..1674b2549f8b 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1988,7 +1988,7 @@ 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 */
--
2.19.1.3.ge56e4f7
