Commit edef1297 authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker
Browse files

SUNRPC: serialize iostats updates 



Occasionally mountstats reports a negative retransmission rate.
Ensure that two RPCs completing concurrently don't confuse the sums
in the transport's op_metrics array.

Since pNFS filelayout can invoke rpc_count_iostats() on another
transport from xprt_release(), we can't rely on simply holding the
transport_lock in xprt_release(). There's nothing for it but hard
serialization. One spin lock per RPC operation should make this as
painless as it can be.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 5d01410f

include/linux/sunrpc/metrics.h

+3 −0
Original line number Diff line number Diff line
@@ -27,10 +27,13 @@ 


#include <linux/seq_file.h>

#include <linux/ktime.h>

#include <linux/spinlock.h>



#define RPC_IOSTATS_VERS	"1.0"



struct rpc_iostats {

	spinlock_t		om_lock;



	/*

	 * These counters give an idea about how many request

	 * transmissions are required, on average, to complete that

net/sunrpc/stats.c

+16 −5
Original line number Diff line number Diff line
@@ -116,7 +116,15 @@ EXPORT_SYMBOL_GPL(svc_seq_show); 
 */

struct rpc_iostats *rpc_alloc_iostats(struct rpc_clnt *clnt)

{

	return kcalloc(clnt->cl_maxproc, sizeof(struct rpc_iostats), GFP_KERNEL);

	struct rpc_iostats *stats;

	int i;



	stats = kcalloc(clnt->cl_maxproc, sizeof(*stats), GFP_KERNEL);

	if (stats) {

		for (i = 0; i < clnt->cl_maxproc; i++)

			spin_lock_init(&stats[i].om_lock);

	}

	return stats;

}

EXPORT_SYMBOL_GPL(rpc_alloc_iostats);
@@ -135,20 +143,21 @@ EXPORT_SYMBOL_GPL(rpc_free_iostats); 
 * rpc_count_iostats - tally up per-task stats

 * @task: completed rpc_task

 * @stats: array of stat structures

 *

 * Relies on the caller for serialization.

 */

void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats)

{

	struct rpc_rqst *req = task->tk_rqstp;

	struct rpc_iostats *op_metrics;

	ktime_t delta;

	ktime_t delta, now;



	if (!stats || !req)

		return;



	now = ktime_get();

	op_metrics = &stats[task->tk_msg.rpc_proc->p_statidx];



	spin_lock(&op_metrics->om_lock);



	op_metrics->om_ops++;

	op_metrics->om_ntrans += req->rq_ntrans;

	op_metrics->om_timeouts += task->tk_timeouts;
@@ -161,8 +170,10 @@ void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats) 


	op_metrics->om_rtt = ktime_add(op_metrics->om_rtt, req->rq_rtt);



	delta = ktime_sub(ktime_get(), task->tk_start);

	delta = ktime_sub(now, task->tk_start);

	op_metrics->om_execute = ktime_add(op_metrics->om_execute, delta);



	spin_unlock(&op_metrics->om_lock);

}

EXPORT_SYMBOL_GPL(rpc_count_iostats);

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