From: Chuck Lever <chuck.lever@xxxxxxxxxx>
Measure a source of thread scheduling inefficiency -- count threads
that were awoken but found that the transport queue had already been
emptied.
An empty transport queue is possible when threads that run between
the wake_up_process() call and the woken thread returning from the
scheduler have pulled all remaining work off the transport queue
using the first svc_xprt_dequeue() in svc_get_next_xprt().
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/linux/sunrpc/svc.h | 1 +
net/sunrpc/svc.c | 2 ++
net/sunrpc/svc_xprt.c | 7 ++++---
3 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 74ea13270679..9dd3b16cc4c2 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -43,6 +43,7 @@ struct svc_pool {
struct percpu_counter sp_threads_woken;
struct percpu_counter sp_threads_timedout;
struct percpu_counter sp_threads_starved;
+ struct percpu_counter sp_threads_no_work;
#define SP_TASK_PENDING (0) /* still work to do even if no
* xprt is queued. */
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 88b7b5fb6d75..b7a02309ecb1 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -518,6 +518,7 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
percpu_counter_init(&pool->sp_threads_woken, 0, GFP_KERNEL);
percpu_counter_init(&pool->sp_threads_timedout, 0, GFP_KERNEL);
percpu_counter_init(&pool->sp_threads_starved, 0, GFP_KERNEL);
+ percpu_counter_init(&pool->sp_threads_no_work, 0, GFP_KERNEL);
}
return serv;
@@ -595,6 +596,7 @@ svc_destroy(struct kref *ref)
percpu_counter_destroy(&pool->sp_threads_woken);
percpu_counter_destroy(&pool->sp_threads_timedout);
percpu_counter_destroy(&pool->sp_threads_starved);
+ percpu_counter_destroy(&pool->sp_threads_no_work);
}
kfree(serv->sv_pools);
kfree(serv);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index ecbccf0d89b9..6c2a702aa469 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -776,9 +776,9 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
if (!time_left)
percpu_counter_inc(&pool->sp_threads_timedout);
-
if (signalled() || kthread_should_stop())
return ERR_PTR(-EINTR);
+ percpu_counter_inc(&pool->sp_threads_no_work);
return ERR_PTR(-EAGAIN);
out_found:
/* Normally we will wait up to 5 seconds for any required
@@ -1445,13 +1445,14 @@ static int svc_pool_stats_show(struct seq_file *m, void *p)
return 0;
}
- seq_printf(m, "%u %llu %llu %llu %llu %llu\n",
+ seq_printf(m, "%u %llu %llu %llu %llu %llu %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_timedout),
- percpu_counter_sum_positive(&pool->sp_threads_starved));
+ percpu_counter_sum_positive(&pool->sp_threads_starved),
+ percpu_counter_sum_positive(&pool->sp_threads_no_work));
return 0;
}
