From 5f07d51751bdee2dbba0a88de8ccb479357f5411 Mon Sep 17 00:00:00 2001 From: Gregor Kopka Date: Wed, 26 Sep 2018 01:29:16 +0200 Subject: [PATCH] Zpool iostat: remove latency/queue scaling Bandwidth and iops are average per second while *_wait are averages per request for latency or, for queue depths, an instantaneous measurement at the end of an interval (according to man zpool). When calculating the first two it makes sense to do x/interval_duration (x being the increase in total bytes or number of requests over the duration of the interval, interval_duration in seconds) to 'scale' from amount/interval_duration to amount/second. But applying the same math for the latter (*_wait latencies/queue) is wrong as there is no interval_duration component in the values (these are time/requests to get to average_time/request or already an absulute number). This bug leads to the only correct continuous *_wait figures for both latencies and queue depths from 'zpool iostat -l/q' being with duration=1 as then the wrong math cancels itself (x/1 is a nop). This removes temporal scaling from latency and queue depth figures. Reviewed-by: Tony Hutter Reviewed-by: Brian Behlendorf Signed-off-by: Gregor Kopka Closes #7945 Closes #7694 --- cmd/zpool/zpool_main.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c index a4fd032123..591e2e5cd1 100644 --- a/cmd/zpool/zpool_main.c +++ b/cmd/zpool/zpool_main.c @@ -3493,7 +3493,7 @@ single_histo_average(uint64_t *histo, unsigned int buckets) static void print_iostat_queues(iostat_cbdata_t *cb, nvlist_t *oldnv, - nvlist_t *newnv, double scale) + nvlist_t *newnv) { int i; uint64_t val; @@ -3523,7 +3523,7 @@ print_iostat_queues(iostat_cbdata_t *cb, nvlist_t *oldnv, format = ZFS_NICENUM_1024; for (i = 0; i < ARRAY_SIZE(names); i++) { - val = nva[i].data[0] * scale; + val = nva[i].data[0]; print_one_stat(val, format, column_width, cb->cb_scripted); } @@ -3532,7 +3532,7 @@ print_iostat_queues(iostat_cbdata_t *cb, nvlist_t *oldnv, static void print_iostat_latency(iostat_cbdata_t *cb, nvlist_t *oldnv, - nvlist_t *newnv, double scale) + nvlist_t *newnv) { int i; uint64_t val; @@ -3562,7 +3562,7 @@ print_iostat_latency(iostat_cbdata_t *cb, nvlist_t *oldnv, /* Print our avg latencies on the line */ for (i = 0; i < ARRAY_SIZE(names); i++) { /* Compute average latency for a latency histo */ - val = single_histo_average(nva[i].data, nva[i].count) * scale; + val = single_histo_average(nva[i].data, nva[i].count); print_one_stat(val, format, column_width, cb->cb_scripted); } free_calc_stats(nva, ARRAY_SIZE(names)); @@ -3701,9 +3701,9 @@ print_vdev_stats(zpool_handle_t *zhp, const char *name, nvlist_t *oldnv, print_iostat_default(calcvs, cb, scale); } if (cb->cb_flags & IOS_LATENCY_M) - print_iostat_latency(cb, oldnv, newnv, scale); + print_iostat_latency(cb, oldnv, newnv); if (cb->cb_flags & IOS_QUEUES_M) - print_iostat_queues(cb, oldnv, newnv, scale); + print_iostat_queues(cb, oldnv, newnv); if (cb->cb_flags & IOS_ANYHISTO_M) { printf("\n"); print_iostat_histos(cb, oldnv, newnv, scale, name);