From: Vincent Fu <vincent.fu@xxxxxxx> 1) Add a description for the lat (min, max, avg, stddev) line 2) Use the old 'IO latencies' description for the lat (nsec/usec/msec) section 3) Fix the description of the 'IO latency' section --- HOWTO | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) diff --git a/HOWTO b/HOWTO index 57d4a39..6ecc0a6 100644 --- a/HOWTO +++ b/HOWTO @@ -3133,9 +3133,9 @@ group) the output looks like:: | 99.99th=[78119] bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100 iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100 - lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79% - lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37% - lat (msec) : 100=0.65% + lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79% + lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37% + lat (msec) : 100=0.65% cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21 IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% @@ -3174,6 +3174,10 @@ writes in the example above). In the order listed, they denote: complete is basically just CPU time (I/O has already been done, see slat explanation). +**lat** + Total latency. Same names as slat and clat, this denotes the time from + when fio created the I/O unit to completion of the I/O operation. + **bw** Bandwidth statistics based on samples. Same names as the xlat stats, but also includes the number of samples taken (**samples**) and an @@ -3185,6 +3189,14 @@ writes in the example above). In the order listed, they denote: **iops** IOPS statistics based on samples. Same names as bw. +**lat (nsec/usec/msec)** + The distribution of I/O completion latencies. This is the time from when + I/O leaves fio and when it gets completed. Unlike the separate + read/write/trim sections above, the data here and in the remaining + sections apply to all I/Os for the reporting group. 250=0.04% means that + 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11% + of the I/Os required 250 to 499us for completion. + **cpu** CPU usage. User and system time, along with the number of context switches this thread went through, usage of system and user time, and @@ -3215,12 +3227,10 @@ writes in the example above). In the order listed, they denote: The number of read/write/trim requests issued, and how many of them were short or dropped. -**IO latencies** - The distribution of I/O completion latencies. This is the time from when - I/O leaves fio and when it gets completed. The numbers follow the same - pattern as the I/O depths, meaning that 2=1.6% means that 1.6% of the - I/O completed within 2 msecs, 20=12.8% means that 12.8% of the I/O took - more than 10 msecs, but less than (or equal to) 20 msecs. +**IO latency** + These values are for `--latency-target` and related options. When + these options are engaged, this section describes the I/O depth required + to meet the specified latency target. .. Example output was based on the following: -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
