From ff8399709e41bf72b4cb145612a0f9a9f7283c83 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 7 May 2010 13:34:47 -0400 Subject: SUNRPC: Replace jiffies-based metrics with ktime-based metrics Currently RPC performance metrics that tabulate elapsed time use jiffies time values. This is problematic on systems that use slow jiffies (for instance 100HZ systems built for paravirtualized environments). It is also a problem for computing precise latency statistics for advanced network transports, such as InfiniBand, that can have round-trip latencies significanly faster than a single clock tick. For the RPC client, adopt the high resolution time stamp mechanism already used by the network layer and blktrace: ktime. We use ktime format time stamps for all internal computations, and convert to milliseconds for presentation. As a result, we need only addition operations in the performance critical paths; multiply/divide is required only for presentation. We could report RTT metrics in microseconds. In fact the mountstats format is versioned to accomodate exactly this kind of interface improvement. For now, however, we'll stay with millisecond precision for presentation to maintain backwards compatibility with the handful of currently deployed user space tools. At a later point, we'll move to an API such as BDI_STATS where a finer timestamp precision can be reported. Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust --- net/sunrpc/stats.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) (limited to 'net/sunrpc/stats.c') diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c index 5785d2037f4..aacd95f0dce 100644 --- a/net/sunrpc/stats.c +++ b/net/sunrpc/stats.c @@ -144,7 +144,7 @@ void rpc_count_iostats(struct rpc_task *task) struct rpc_rqst *req = task->tk_rqstp; struct rpc_iostats *stats; struct rpc_iostats *op_metrics; - long rtt, execute, queue; + ktime_t delta; if (!task->tk_client || !task->tk_client->cl_metrics || !req) return; @@ -159,20 +159,13 @@ void rpc_count_iostats(struct rpc_task *task) op_metrics->om_bytes_sent += task->tk_bytes_sent; op_metrics->om_bytes_recv += req->rq_reply_bytes_recvd; - queue = (long)req->rq_xtime - task->tk_start; - if (queue < 0) - queue = -queue; - op_metrics->om_queue += queue; + delta = ktime_sub(req->rq_xtime, task->tk_start); + op_metrics->om_queue = ktime_add(op_metrics->om_queue, delta); - rtt = task->tk_rtt; - if (rtt < 0) - rtt = -rtt; - op_metrics->om_rtt += rtt; + op_metrics->om_rtt = ktime_add(op_metrics->om_rtt, task->tk_rtt); - execute = (long)jiffies - task->tk_start; - if (execute < 0) - execute = -execute; - op_metrics->om_execute += execute; + delta = ktime_sub(ktime_get(), task->tk_start); + op_metrics->om_execute = ktime_add(op_metrics->om_execute, delta); } static void _print_name(struct seq_file *seq, unsigned int op, @@ -186,8 +179,6 @@ static void _print_name(struct seq_file *seq, unsigned int op, seq_printf(seq, "\t%12u: ", op); } -#define MILLISECS_PER_JIFFY (1000 / HZ) - void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt) { struct rpc_iostats *stats = clnt->cl_metrics; @@ -214,9 +205,9 @@ void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt) metrics->om_timeouts, metrics->om_bytes_sent, metrics->om_bytes_recv, - metrics->om_queue * MILLISECS_PER_JIFFY, - metrics->om_rtt * MILLISECS_PER_JIFFY, - metrics->om_execute * MILLISECS_PER_JIFFY); + ktime_to_ms(metrics->om_queue), + ktime_to_ms(metrics->om_rtt), + ktime_to_ms(metrics->om_execute)); } } EXPORT_SYMBOL_GPL(rpc_print_iostats); -- cgit v1.2.3-18-g5258