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| author | Trond Myklebust <trond.myklebust@primarydata.com> | 2014-07-25 05:59:31 +0200 |
|---|---|---|
| committer | J. Bruce Fields <bfields@redhat.com> | 2014-07-29 22:10:15 +0200 |
| commit | 0971374e2818eef6ebdbd7a37acf6ab7e98ac06c (patch) | |
| tree | 87ca80081f794d3b18bc301dc570b9403f39ee4f /net | |
| parent | nfsd: remove dl_fh field from struct nfs4_delegation (diff) | |
| download | linux-0971374e2818eef6ebdbd7a37acf6ab7e98ac06c.tar.xz linux-0971374e2818eef6ebdbd7a37acf6ab7e98ac06c.zip | |
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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sunrpc/svc_xprt.c | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index b4737fbdec13..9cfa391e2bd0 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -23,6 +23,7 @@ static int svc_deferred_recv(struct svc_rqst *rqstp); static struct cache_deferred_req *svc_defer(struct cache_req *req); static void svc_age_temp_xprts(unsigned long closure); static void svc_delete_xprt(struct svc_xprt *xprt); +static void svc_xprt_do_enqueue(struct svc_xprt *xprt); /* apparently the "standard" is that clients close * idle connections after 5 minutes, servers after @@ -222,11 +223,12 @@ static void svc_xprt_received(struct svc_xprt *xprt) if (!test_bit(XPT_BUSY, &xprt->xpt_flags)) return; /* As soon as we clear busy, the xprt could be closed and - * 'put', so we need a reference to call svc_xprt_enqueue with: + * 'put', so we need a reference to call svc_xprt_do_enqueue with: */ svc_xprt_get(xprt); + smp_mb__before_atomic(); clear_bit(XPT_BUSY, &xprt->xpt_flags); - svc_xprt_enqueue(xprt); + svc_xprt_do_enqueue(xprt); svc_xprt_put(xprt); } @@ -335,12 +337,7 @@ static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt) return false; } -/* - * Queue up a transport with data pending. If there are idle nfsd - * processes, wake 'em up. - * - */ -void svc_xprt_enqueue(struct svc_xprt *xprt) +static void svc_xprt_do_enqueue(struct svc_xprt *xprt) { struct svc_pool *pool; struct svc_rqst *rqstp; @@ -398,6 +395,18 @@ void svc_xprt_enqueue(struct svc_xprt *xprt) out_unlock: spin_unlock_bh(&pool->sp_lock); } + +/* + * Queue up a transport with data pending. If there are idle nfsd + * processes, wake 'em up. + * + */ +void svc_xprt_enqueue(struct svc_xprt *xprt) +{ + if (test_bit(XPT_BUSY, &xprt->xpt_flags)) + return; + svc_xprt_do_enqueue(xprt); +} EXPORT_SYMBOL_GPL(svc_xprt_enqueue); /* |