aisloader: '--subdir' vs prefix (clarify)

Signed-off-by: Alex Aizman <alex.aizman@gmail.com>

bench/tools/aisloader/run.go

@@ -585,8 +585,11 @@ func addCmdLine(f *flag.FlagSet, p *params) {
 		"when true, generate object names of 32 random characters. This option is ignored when loadernum is defined")
 	f.BoolVar(&p.randomProxy, "randomproxy", false,
 		"when true, select random gateway (\"proxy\") to execute I/O request")
-	f.StringVar(&p.subDir, "subdir", "", "when writing: virtual destination directory for all aisloader-generated objects;\n"+
-		"when listing: list objects with names that have the specified prefix (that may or may not be a virtual directory")
+	f.StringVar(&p.subDir, "subdir", "", "For GET requests, '-subdir' is a prefix that may or may not be an actual _virtual directory_;\n"+
+		"For PUTs, '-subdir' is a virtual destination directory for all aisloader-generated objects;\n"+
+		"See also:\n"+
+		"\t- closely related CLI '--prefix' option: "+cmn.GitHubHome+"/blob/main/docs/cli/object.md\n"+
+		"\t- virtual directories:                   "+cmn.GitHubHome+"/blob/main/docs/howto_virt_dirs.md")
 	f.Uint64Var(&p.putShards, "putshards", 0, "spread generated objects over this many subdirectories (max 100k)")
 	f.BoolVar(&p.uniqueGETs, "uniquegets", true,
 		"when true, GET objects randomly and equally. Meaning, make sure *not* to GET some objects more frequently than the others")

docs/aisloader.md

@@ -98,7 +98,7 @@ For the most recently updated command-line options and examples, please run `ais
 | -statsdport | `int` | StatsD UDP port | `8125` |
 | -statsdprobe | `bool` | Test-probe StatsD server prior to benchmarks | `true` |
 | -statsinterval | `int` | Interval in seconds to print performance counters; 0 - disabled | `10` |
-| -subdir | `string` | Virtual destination directory for all aisloader-generated objects | `""` |
+| -subdir | `string` | For GET requests, `-subdir` is a prefix that may or may not be an actual [virtual directory](/docs/howto_virt_dirs.md). For PUT, `-subdir` is a virtual destination directory for all aisloader-generated objects. See closely related [CLI](/docs/cli/object.md) `--prefix` option. | `""` |
 | -test-probe | `bool`| Test StatsD server prior to running benchmarks | `false` |
 | -timeout | `string` | Client HTTP timeout; `0` = infinity) | `10m` |
 | -tmpdir | `string` | Local directory to store temporary files | `/tmp/ais` |