Hello, we want to make experiments with smaller TX ring sizes to evaluate how much the throughput decreases. We are using two distinct NICs on two different PCs:
Ethernet controller: Intel Corporation Ethernet Connection (2) I219-LM (rev 31) and Ethernet controller: Intel Corporation Ethernet Connection I217-LM (rev 04) both using the e1000e kernel module (kernel 4.8.7, module version 3.2.6) We recompiled the e1000e module with the following patch: --- linux-4.8/drivers/net/ethernet/intel/e1000e/e1000.h.orig 2016-11-15 15:42:18.181412740 +0100 +++ linux-4.8/drivers/net/ethernet/intel/e1000e/e1000.h 2016-11-15 15:42:55.961607611 +0100 @@ -64,7 +64,7 @@ /* Tx/Rx descriptor defines */ #define E1000_DEFAULT_TXD 256 #define E1000_MAX_TXD 4096 -#define E1000_MIN_TXD 64 +#define E1000_MIN_TXD 4 #define E1000_DEFAULT_RXD 256 #define E1000_MAX_RXD 4096 Then, we set the TX ring size to 16 with ethtool: sudo ethtool -G <iface> tx 16 The change was applied (as confirmed by ethtool -g) but the whole system freezed a few seconds later. This happens every time we set the tx ring size to 16. We cannot ping the machine nor ssh into it, we can only force shutdown. Looking at the journal log (systemd) there is no sign of the freeze. We would like to know if there are known issues that prevent setting the TX ring size below a certain threshold. Also, we would appreciate it very much if someone could advise what to do to investigate/solve the issue we are facing. Thanks a lot in advance for any help. Bests, Stefano
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