ff8399709e
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 <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
91 lines
3.2 KiB
C
91 lines
3.2 KiB
C
/*
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* linux/include/linux/sunrpc/metrics.h
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*
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* Declarations for RPC client per-operation metrics
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*
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* Copyright (C) 2005 Chuck Lever <cel@netapp.com>
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*
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* RPC client per-operation statistics provide latency and retry
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* information about each type of RPC procedure in a given RPC program.
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* These statistics are not for detailed problem diagnosis, but simply
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* to indicate whether the problem is local or remote.
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*
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* These counters are not meant to be human-readable, but are meant to be
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* integrated into system monitoring tools such as "sar" and "iostat". As
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* such, the counters are sampled by the tools over time, and are never
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* zeroed after a file system is mounted. Moving averages can be computed
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* by the tools by taking the difference between two instantaneous samples
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* and dividing that by the time between the samples.
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*
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* The counters are maintained in a single array per RPC client, indexed
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* by procedure number. There is no need to maintain separate counter
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* arrays per-CPU because these counters are always modified behind locks.
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*/
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#ifndef _LINUX_SUNRPC_METRICS_H
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#define _LINUX_SUNRPC_METRICS_H
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#include <linux/seq_file.h>
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#include <linux/ktime.h>
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#define RPC_IOSTATS_VERS "1.0"
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struct rpc_iostats {
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/*
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* These counters give an idea about how many request
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* transmissions are required, on average, to complete that
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* particular procedure. Some procedures may require more
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* than one transmission because the server is unresponsive,
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* the client is retransmitting too aggressively, or the
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* requests are large and the network is congested.
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*/
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unsigned long om_ops, /* count of operations */
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om_ntrans, /* count of RPC transmissions */
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om_timeouts; /* count of major timeouts */
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/*
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* These count how many bytes are sent and received for a
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* given RPC procedure type. This indicates how much load a
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* particular procedure is putting on the network. These
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* counts include the RPC and ULP headers, and the request
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* payload.
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*/
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unsigned long long om_bytes_sent, /* count of bytes out */
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om_bytes_recv; /* count of bytes in */
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/*
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* The length of time an RPC request waits in queue before
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* transmission, the network + server latency of the request,
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* and the total time the request spent from init to release
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* are measured.
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*/
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ktime_t om_queue, /* queued for xmit */
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om_rtt, /* RPC RTT */
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om_execute; /* RPC execution */
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} ____cacheline_aligned;
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struct rpc_task;
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struct rpc_clnt;
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/*
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* EXPORTed functions for managing rpc_iostats structures
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*/
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#ifdef CONFIG_PROC_FS
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struct rpc_iostats * rpc_alloc_iostats(struct rpc_clnt *);
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void rpc_count_iostats(struct rpc_task *);
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void rpc_print_iostats(struct seq_file *, struct rpc_clnt *);
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void rpc_free_iostats(struct rpc_iostats *);
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#else /* CONFIG_PROC_FS */
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static inline struct rpc_iostats *rpc_alloc_iostats(struct rpc_clnt *clnt) { return NULL; }
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static inline void rpc_count_iostats(struct rpc_task *task) {}
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static inline void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt) {}
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static inline void rpc_free_iostats(struct rpc_iostats *stats) {}
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#endif /* CONFIG_PROC_FS */
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#endif /* _LINUX_SUNRPC_METRICS_H */
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