X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=8a7cb1aac380973900a32884f08c64df3cb41a02;hp=b535177c9abb13848346af93bc24b8a186ede983;hb=08b2b386736e9f60a342092ca4b3e6990eab5c2b;hpb=589e88b7d96e8ea18f3257558fd1e00d320cef7d diff --git a/HOWTO b/HOWTO index b535177c..8a7cb1aa 100644 --- a/HOWTO +++ b/HOWTO @@ -505,19 +505,19 @@ Parameter types prefixes. To specify power-of-10 decimal values defined in the International System of Units (SI): - * *ki* -- means kilo (K) or 1000 - * *mi* -- means mega (M) or 1000**2 - * *gi* -- means giga (G) or 1000**3 - * *ti* -- means tera (T) or 1000**4 - * *pi* -- means peta (P) or 1000**5 + * *Ki* -- means kilo (K) or 1000 + * *Mi* -- means mega (M) or 1000**2 + * *Gi* -- means giga (G) or 1000**3 + * *Ti* -- means tera (T) or 1000**4 + * *Pi* -- means peta (P) or 1000**5 To specify power-of-2 binary values defined in IEC 80000-13: - * *k* -- means kibi (Ki) or 1024 - * *m* -- means mebi (Mi) or 1024**2 - * *g* -- means gibi (Gi) or 1024**3 - * *t* -- means tebi (Ti) or 1024**4 - * *p* -- means pebi (Pi) or 1024**5 + * *K* -- means kibi (Ki) or 1024 + * *M* -- means mebi (Mi) or 1024**2 + * *G* -- means gibi (Gi) or 1024**3 + * *T* -- means tebi (Ti) or 1024**4 + * *P* -- means pebi (Pi) or 1024**5 With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite from those specified in the SI and IEC 80000-13 standards to provide @@ -2030,6 +2030,21 @@ I/O depth 16 requests, it will let the depth drain down to 4 before starting to fill it again. +.. option:: serialize_overlap=bool + + Serialize in-flight I/Os that might otherwise cause or suffer from data races. + When two or more I/Os are submitted simultaneously, there is no guarantee that + the I/Os will be processed or completed in the submitted order. Further, if + two or more of those I/Os are writes, any overlapping region between them can + become indeterminate/undefined on certain storage. These issues can cause + verification to fail erratically when at least one of the racing I/Os is + changing data and the overlapping region has a non-zero size. Setting + ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly + serializing in-flight I/Os that have a non-zero overlap. Note that setting + this option can reduce both performance and the `:option:iodepth` achieved. + Additionally this option does not work when :option:`io_submit_mode` is set to + offload. Default: false. + .. option:: io_submit_mode=str This option controls how fio submits the I/O to the I/O engine. The default @@ -2605,7 +2620,6 @@ Verification Enable experimental verification. - Steady state ~~~~~~~~~~~~ @@ -3363,6 +3377,27 @@ minimal output v3, separated by semicolons:: terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util +JSON+ output +------------ + +The `json+` output format is identical to the `json` output format except that it +adds a full dump of the completion latency bins. Each `bins` object contains a +set of (key, value) pairs where keys are latency durations and values count how +many I/Os had completion latencies of the corresponding duration. For example, +consider: + + "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... } + +This data indicates that one I/O required 87,552ns to complete, two I/Os required +100,864ns to complete, and 7529 I/Os required 107,008ns to complete. + +Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes +json+ output and generates CSV-formatted latency data suitable for plotting. + +The latency durations actually represent the midpoints of latency intervals. +For details refer to stat.h. + + Trace file format -----------------