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Diffstat (limited to 'cddl/contrib/dtracetoolkit/Examples/rfsio_example.txt')
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diff --git a/cddl/contrib/dtracetoolkit/Examples/rfsio_example.txt b/cddl/contrib/dtracetoolkit/Examples/rfsio_example.txt new file mode 100644 index 0000000..858ddf8 --- /dev/null +++ b/cddl/contrib/dtracetoolkit/Examples/rfsio_example.txt @@ -0,0 +1,82 @@ +The following are demonstrations of the rfsio.d script. + + + +Here we trace file read() activity that has fully missed the cache and +must be read from disk, + + # ./rfsio.d + + Read IOPS (count) + / logical 7 + /extra1 physical 162 + /boot logical 235 + /boot physical 410 + /extra1 logical 9514 + + Read Bandwidth (bytes) + / logical 533 + /boot logical 1502386 + /boot physical 1512960 + /extra1 physical 97153024 + /extra1 logical 97228668 + + Total File System miss-rate: 100% + ^C + +The miss rate of 100% means that all of the file system activity missed +the cache, and had to read from disk. + + + +The following demonstrates file read() activity to the root filesystem +that mostly returned from the file system cache. + + # ./rfsio.d + + Read IOPS (count) + / physical 1 + /extra1 physical 9 + /devices logical 9 + / logical 15 + /extra1 logical 4096 + + Read Bandwidth (bytes) + /devices logical 9 + / logical 949 + / physical 8192 + /extra1 physical 917504 + /extra1 logical 4194304 + + Total File System miss-rate: 22% + ^C + +The total miss-rate was 22%, which is based on the bytes transferred that +missed the cache. + + + + +Now for an unusual demonstration, + + # ./rfsio.d + + Read IOPS (count) + /devices logical 1 + / logical 10 + /extra1 physical 106 + /extra1 logical 6337 + + Read Bandwidth (bytes) + /devices logical 2 + / logical 961 + /extra1 logical 64846450 + /extra1 physical 66151424 + + Total File System miss-rate: 102% + ^C + +Here the miss-rate is 102%, which indicates that more data was read from +disk than was requested; this can occur due to UFS read-ahead, which +assists the performance of sequential disk activity at the small risk of +reading too much data. |