It doesn't seem memory is an issue.
The whole dump is about the same.
The MemFree and MemAvailable doesn't change much.
I talked with Marcelo about this one.
He said it might be related with cacheline. the new field distroyed
the prior cacheline. So on top of commit 826d253d57b1, pls only add
+ unsigned long prsctp_param;
to the end of struct sctp_chunk, then try.
if 1) still doesn't work, I may think about to drop prsctp_param in
sctp_chunk, and reuse msg->expire_at. as for sent_count, I will
put it to the mem hole of sctp_chunk.
So pls also try the attachment patch, on top of commit a6c2f792873a