From 0971374e2818eef6ebdbd7a37acf6ab7e98ac06c Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Thu, 24 Jul 2014 23:59:31 -0400
Subject: [PATCH] SUNRPC: Reduce contention in svc_xprt_enqueue()

Ensure that all calls to svc_xprt_enqueue() except svc_xprt_received()
check the value of XPT_BUSY, before attempting to grab spinlocks etc.
This is to avoid situations such as the following "perf" trace,
which shows heavy contention on the pool spinlock:

    54.15%            nfsd  [kernel.kallsyms]        [k] _raw_spin_lock_bh
                      |
                      --- _raw_spin_lock_bh
                         |
                         |--71.43%-- svc_xprt_enqueue
                         |          |
                         |          |--50.31%-- svc_reserve
                         |          |
                         |          |--31.35%-- svc_xprt_received
                         |          |
                         |          |--18.34%-- svc_tcp_data_ready
...

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
Reading git-format-patch failed