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queue_stats.stp
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# qstats.stp: Queue statistics gathering tapset /* <tapsetdescription> * The queue_stats tapset provides functions that, * given notifications of elementary queuing events (wait, run, done), * tracks averages such as queue length, service and wait times, * utilization. * * The functions qs_wait(), qs_run(), and qs_done() should be called * from appropriate probes, in sequence. * * Functions with the prefix qsq_ are for querying the statistics averaged * since the first queue operation (or when qsq_start() was called). * Since statistics are often fractional, a scale parameter is used to * multiply the result to a more useful scale. For some fractions, a scale * of 100 will usefully return percentage numbers. * </tapsetdescription> */ # ------------------------------------------------------------------------ # The default timing function: microseconds. This function could # go into a separate file (say, qstats_qs_time.stp), so that a user # script can override it with another definition. /* XXX: docstring */ function qs_time () { return gettimeofday_us () } # ------------------------------------------------------------------------ @__private30 global qs_wtime, qs_wlentime, qs_wcount @__private30 global qs_rtime, qs_rlentime, qs_rcount @__private30 global qs_stime, qs_utime, qs_dcount # ------------------------------------------------------------------------ @__private30 function _qs_update (qname) { now = qs_time () then = qs_utime[qname]; if (! then) { then = now } delta = now-then qs_wtime[qname] += qs_wcount[qname] ? delta : 0 qs_wlentime[qname] += qs_wcount[qname] * delta qs_rtime[qname] += qs_rcount[qname] ? delta : 0 qs_rlentime[qname] += qs_rcount[qname] * delta qs_utime[qname] = now } /** * sfunction qs_wait - Function to record enqueue requests * @qname: the name of the queue requesting enqueue * * Description: This function records that a new request * was enqueued for the given queue name. */ function qs_wait (qname:string) { # enqueueing request _qs_update (qname) qs_wcount[qname] ++ } /** * sfunction qs_run - Function to record being moved from wait queue to being serviced * @qname: the name of the service being moved and started * * Description: This function records that the previous enqueued * request was removed from the given wait queue and is now * being serviced. */ function qs_run (qname:string) { # starting to service request _qs_update (qname) if (qs_wcount[qname] > 0) { qs_wcount[qname] -- qs_rcount[qname] ++ } } /** * sfunction qs_done - Function to record finishing request * @qname: the name of the service that finished * * Description: This function records that a request * originally from the given queue has completed being * serviced. */ function qs_done (qname:string) { # done servicing request _qs_update (qname) if (qs_rcount[qname] > 0) { qs_rcount[qname] -- qs_dcount[qname] ++ } } # ------------------------------------------------------------------------ /** * sfunction qsq_start - Function to reset the stats for a queue * @qname: the name of the service that finished * * Description: This function resets the statistics counters for the given * queue, and restarts tracking from the moment the function was called. * This function is also used to create intialize a queue. */ function qsq_start (qname:string) { # reset statistics for new baseline qs_rcount[qname] = 0 delete qs_rtime[qname] delete qs_rlentime[qname] qs_wcount[qname] = 0 delete qs_wtime[qname] delete qs_wlentime[qname] delete qs_dcount[qname] delete qs_utime[qname] qs_stime[qname] = qs_time () } # ------------------------------------------------------------------------ # Various query functions. Each returns the average, taken over the time # interval from the last qsq_start(). Most deal with fractions, and so # also take a scale parameter (use 100 for percent). /** * sfunction qsq_utilization - Fraction of time that any request was being serviced * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the average time in microseconds * that at least one request was being serviced. */ function qsq_utilization:long (qname:string, scale:long) { _qs_update (qname) elapsed = qs_time() - qs_stime[qname] return (scale * qs_rtime[qname]) / elapsed } # fraction of time that any request was blocked in the wait queue /** * sfunction qsq_blocked - Returns the time reqest was on the wait queue * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the fraction of elapsed time during * which one or more requests were on the wait queue. */ function qsq_blocked:long (qname:string, scale:long) { _qs_update (qname) elapsed = qs_time() - qs_stime[qname] return (scale * qs_wtime[qname]) / elapsed } # length of wait queue /** * sfunction qsq_wait_queue_length - length of wait queue * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the average length of the wait queue */ function qsq_wait_queue_length:long (qname:string, scale:long) { _qs_update (qname) elapsed = qs_time() - qs_stime[qname] return (scale * qs_wlentime[qname]) / elapsed } /** * sfunction qsq_service_time - Amount of time per request service * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the average time in microseconds * required to service a request once it is removed from the wait queue. */ function qsq_service_time:long (qname:string, scale:long) { _qs_update (qname) return (scale * qs_rlentime[qname]) / qs_dcount[qname] } /** * sfunction qsq_wait_time - Amount of time in queue + service per request * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the average time in microseconds * that it took for a request to be serviced (qs_wait() to qa_done()). */ function qsq_wait_time:long (qname:string, scale:long) { _qs_update (qname) return (scale * (qs_rlentime[qname] + qs_wlentime[qname])) / qs_dcount[qname] } /** * sfunction qsq_throughput - Number of requests served per unit time * @qname: queue name * @scale: scale variable to take account for interval fraction * * Description: This function returns the average number or requests * served per microsecond. */ function qsq_throughput:long (qname:string, scale:long) { _qs_update (qname) elapsed = qs_time() - qs_stime[qname] return (scale * qs_dcount[qname]) / elapsed } # ------------------------------------------------------------------------ /** * sfunction qsq_print - Prints a line of statistics for the given queue * @qname: queue name * * Description: This function prints a line containing the following * statistics for the given queue: * the queue name, * the average rate of requests per second, * the average wait queue length, * the average time on the wait queue, * the average time to service a request, * the percentage of time the wait queue was used, * and the percentage of time request was being serviced. */ function qsq_print (qname:string) { qt = qsq_throughput (qname, 1000000000) # 1000 * (number of requests served per second) qwl = qsq_wait_queue_length (qname, 1000) printf("%s: %d.%03d ops/s, %d.%03d qlen, %d await, %d svctm, %d%% wait, %d%% util\n", qname, qt/1000, qt%1000, qwl/1000, qwl%1000, qsq_wait_time (qname, 1), qsq_service_time (qname, 1), qsq_blocked (qname, 100), qsq_utilization (qname, 100)) } /* What follows in an example form src/testsuite/systemtap.samples/queue_demo.stp * It uses the randomize feature of the timer probe to simulate queuing activity. * * probe begin { * qsq_start ("block-read") * qsq_start ("block-write") * } * * probe timer.ms(3500), end { * qsq_print ("block-read") * qsq_start ("block-read") * qsq_print ("block-write") * qsq_start ("block-write") * } * * probe timer.ms(10000) { * exit() * } * * // synthesize queue work/service using three randomized "threads" for each queue. * global tc * * function qs_doit (thread, name) { * n = tc[thread] = (tc[thread]+1) % 3 //per-thread state counter * if (n==1) qs_wait (name) * else if (n==2) qs_run (name) * else if (n==0) qs_done (name) * } * * probe timer.ms(100).randomize(100) { qs_doit (0, "block-read") } * probe timer.ms(100).randomize(100) { qs_doit (1, "block-read") } * probe timer.ms(100).randomize(100) { qs_doit (2, "block-read") } * probe timer.ms(100).randomize(100) { qs_doit (3, "block-write") } * probe timer.ms(100).randomize(100) { qs_doit (4, "block-write") } * probe timer.ms(100).randomize(100) { qs_doit (5, "block-write") } * * //This prints: * block-read: 9 ops/s, 1.090 qlen, 215749 await, 96382 svctm, 69% wait, 64% util * block-write: 9 ops/s, 0.992 qlen, 208485 await, 103150 svctm, 69% wait, 61% util * block-read: 9 ops/s, 0.968 qlen, 197411 await, 97762 svctm, 63% wait, 63% util * block-write: 8 ops/s, 0.930 qlen, 202414 await, 93870 svctm, 60% wait, 56% util * block-read: 8 ops/s, 0.744 qlen, 192957 await, 99995 svctm, 58% wait, 62% util * block-write: 9 ops/s, 0.861 qlen, 193857 await, 101573 svctm, 56% wait, 64% util */