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SUNRPC: serialize iostats updates

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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: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2014-11-08 20:15:09 -05:00 committed by Anna Schumaker
parent 5d01410fe4
commit edef1297f3
2 changed files with 19 additions and 5 deletions
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3
include/linux/sunrpc/metrics.h
View File

@ -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

21
net/sunrpc/stats.c
View File

@ -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);