On Wed, 2015-10-28 at 06:24 -0700, Eric Dumazet wrote:

Before I take a deep look at your suggestion, are you sure plain use of
include/linux/percpu-refcount.h infra is not possible for struct cred ?

BTW, I am not convinced we need to spend so much energy and per-cpu
memory for struct cred refcount.

The big problem is fd array spinlock of course and bitmap search for
POSIX compliance.

The cache line trashing in struct cred is a minor one ;)