syslog: kernel: [ 1241.147934] TCP: ens192: Driver has suspect GRO implementation, TCP performance may be compromised

Question

in Debian 9 running into esxi 6.5 from three days ago the syslog shows this message:

kernel: [ 1241.147934] TCP: ens192: Driver has suspect GRO implementation, TCP performance may be compromised.

But today the virtual machine has crash three times.

I'm not sure that the problem is this messager or not.

heeeelp!

Solution

A Red Hat knowledge base article explains this message:

If calculated MSS (Maximum Segment Value) is higher than Advertised MSS, then set the new MSS to 'Advertised MSS'. In earlier kernels, this was not [done] and could have caused performance issues while GRO (Receive Offload) was used. It's based on these MSS values, TCP window size is determined for data transfer.

This isn't likely to be causing a crash, though as noted the performance of TCP connections may suffer slightly.

Red Hat backported a fix into its kernel for RHEL 7.4, but Debian probably has not done so. And besides, as Red Hat also says:

This message can be treated as informational only and as a warning one which can be safely ignored.