Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-ie0-f171.google.com ([209.85.223.171]:46301 "EHLO mail-ie0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751248AbaGYD7X (ORCPT ); Thu, 24 Jul 2014 23:59:23 -0400 Received: by mail-ie0-f171.google.com with SMTP id at1so3167284iec.16 for ; Thu, 24 Jul 2014 20:59:23 -0700 (PDT) From: Trond Myklebust To: Bruce Fields Cc: linux-nfs@vger.kernel.org Subject: [PATCH 1/3] SUNRPC: Reduce contention in svc_xprt_enqueue() Date: Thu, 24 Jul 2014 23:59:31 -0400 Message-Id: <1406260773-16231-1-git-send-email-trond.myklebust@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 --- net/sunrpc/svc_xprt.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index b4737fbdec13..54a761fa6351 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_clear_bit(); 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); /* -- 1.9.3