linux-kernel - [PATCH 4/4] sunrpc: keep a count of when there are no threads available

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Message-Id: <20250306-nfsd-tracepoints-v1-4-4405bf41b95f@kernel.org>
Date: Thu, 06 Mar 2025 07:38:16 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>, 
 Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, 
 Tom Talpey <tom@...pey.com>, Trond Myklebust <trondmy@...nel.org>, 
 Anna Schumaker <anna@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Cc: Sargun Dillon <sargun@...a.com>, linux-nfs@...r.kernel.org, 
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 4/4] sunrpc: keep a count of when there are no threads
 available

Add a new percpu counter and pool_stat that can track how often the
kernel went to wake up a thread, but they all were busy.

Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 include/linux/sunrpc/svc.h | 1 +
 net/sunrpc/svc.c           | 4 +++-
 net/sunrpc/svc_xprt.c      | 7 ++++---
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 74658cca0f38f21e2673c84c7bcae948ff7feea6..179dbfc86887374e1a0a2b669c5839cb622dd3f5 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -44,6 +44,7 @@ struct svc_pool {
 	struct percpu_counter	sp_messages_arrived;
 	struct percpu_counter	sp_sockets_queued;
 	struct percpu_counter	sp_threads_woken;
+	struct percpu_counter	sp_no_threads_avail;
 
 	unsigned long		sp_flags;
 } ____cacheline_aligned_in_smp;
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e7f9c295d13c03bf28a5eeec839fd85e24f5525f..789f08022aec210b6df08036997ef801d3c73ac8 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -545,6 +545,7 @@ __svc_create(struct svc_program *prog, int nprogs, struct svc_stat *stats,
 		percpu_counter_init(&pool->sp_messages_arrived, 0, GFP_KERNEL);
 		percpu_counter_init(&pool->sp_sockets_queued, 0, GFP_KERNEL);
 		percpu_counter_init(&pool->sp_threads_woken, 0, GFP_KERNEL);
+		percpu_counter_init(&pool->sp_no_threads_avail, 0, GFP_KERNEL);
 	}
 
 	return serv;
@@ -629,6 +630,7 @@ svc_destroy(struct svc_serv **servp)
 		percpu_counter_destroy(&pool->sp_messages_arrived);
 		percpu_counter_destroy(&pool->sp_sockets_queued);
 		percpu_counter_destroy(&pool->sp_threads_woken);
+		percpu_counter_destroy(&pool->sp_no_threads_avail);
 	}
 	kfree(serv->sv_pools);
 	kfree(serv);
@@ -756,7 +758,7 @@ void svc_pool_wake_idle_thread(struct svc_pool *pool)
 		return;
 	}
 	rcu_read_unlock();
-
+	percpu_counter_inc(&pool->sp_no_threads_avail);
 }
 EXPORT_SYMBOL_GPL(svc_pool_wake_idle_thread);
 
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index ae25405d8bd22672a361d1fd3adfdcebb403f90f..b2c5a74e4609e8f4a3f5f4637dd9b46b40b79324 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -1451,15 +1451,16 @@ static int svc_pool_stats_show(struct seq_file *m, void *p)
 	struct svc_pool *pool = p;
 
 	if (p == SEQ_START_TOKEN) {
-		seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken threads-timedout\n");
+		seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken threads-timedout no-threads-avail\n");
 		return 0;
 	}
 
-	seq_printf(m, "%u %llu %llu %llu 0\n",
+	seq_printf(m, "%u %llu %llu %llu 0 %llu\n",
 		   pool->sp_id,
 		   percpu_counter_sum_positive(&pool->sp_messages_arrived),
 		   percpu_counter_sum_positive(&pool->sp_sockets_queued),
-		   percpu_counter_sum_positive(&pool->sp_threads_woken));
+		   percpu_counter_sum_positive(&pool->sp_threads_woken),
+		   percpu_counter_sum_positive(&pool->sp_no_threads_avail));
 
 	return 0;
 }

-- 
2.48.1