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diff --git a/cddl/contrib/dtracetoolkit/dist/Examples/seeksize_example.txt b/cddl/contrib/dtracetoolkit/dist/Examples/seeksize_example.txt new file mode 100644 index 0000000..ba41a87 --- /dev/null +++ b/cddl/contrib/dtracetoolkit/dist/Examples/seeksize_example.txt @@ -0,0 +1,197 @@ +The following are examples of seeksize.d. + +seeksize.d records disk head seek size for each operation by process. +This allows up to identify processes that are causing "random" disk +access and those causing "sequential" disk access. + +It is desirable for processes to be accesing the disks in large +sequential operations. By using seeksize.d and bitesize.d we can +identify this behaviour. + + + +In this example we read through a large file by copying it to a +remote server. Most of the seek sizes are zero, indicating sequential +access - and we would expect good performance from the disks +under these conditions, + +# ./seeksize.d +Tracing... Hit Ctrl-C to end. +^C + + 22349 scp /dl/sol-10-b63-x86-v1.iso mars:\0 + + value ------------- Distribution ------------- count + -1 | 0 + 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 726 + 1 | 0 + 2 | 0 + 4 | 0 + 8 |@ 13 + 16 | 4 + 32 | 0 + 64 | 0 + 128 | 2 + 256 | 3 + 512 | 4 + 1024 | 4 + 2048 | 3 + 4096 | 0 + 8192 | 3 + 16384 | 0 + 32768 | 1 + 65536 | 0 + + + +In this example we run find. The disk operations are fairly scattered, +as illustrated below by the volume of non sequential reads, + +# ./seeksize.d +Tracing... Hit Ctrl-C to end. +^C + + 22399 find /var/sadm/pkg/\0 + + value ------------- Distribution ------------- count + -1 | 0 + 0 |@@@@@@@@@@@@@ 1475 + 1 | 0 + 2 | 44 + 4 |@ 77 + 8 |@@@ 286 + 16 |@@ 191 + 32 |@ 154 + 64 |@@ 173 + 128 |@@ 179 + 256 |@@ 201 + 512 |@@ 186 + 1024 |@@ 236 + 2048 |@@ 201 + 4096 |@@ 274 + 8192 |@@ 243 + 16384 |@ 154 + 32768 |@ 113 + 65536 |@@ 182 + 131072 |@ 81 + 262144 | 0 + + + + +I found the following interesting. This time I gzipp'd the large file. +While zipping, the process is reading from one location and writing +to another. One might expect that as the program toggles between +reading from one location and writing to another, that often the +distance would be the same (depending on where UFS puts the new file), + +# ./seeksize.d +Tracing... Hit Ctrl-C to end. +^C + + 22368 gzip sol-10-b63-x86-v1.iso\0 + + value ------------- Distribution ------------- count + -1 | 0 + 0 |@@@@@@@@@@@@ 353 + 1 | 0 + 2 | 0 + 4 | 0 + 8 | 7 + 16 | 4 + 32 | 2 + 64 | 4 + 128 | 14 + 256 | 3 + 512 | 3 + 1024 | 5 + 2048 | 1 + 4096 | 0 + 8192 | 3 + 16384 | 1 + 32768 | 1 + 65536 | 1 + 131072 | 1 + 262144 |@@@@@@@@ 249 + 524288 | 1 + 1048576 | 2 + 2097152 | 1 + 4194304 | 2 + 8388608 |@@@@@@@@@@@@@@@@@@ 536 + 16777216 | 0 + + + + +The following example compares the operation of "find" with "tar". +Both are reading from the same location, and we would expect that +both programs would generally need to do the same number of seeks +to navigate the direttory tree (depending on caching); and tar +causing extra operations as it reads the file contents as well, + +# ./seeksize.d +Tracing... Hit Ctrl-C to end. +^C + + PID CMD + 22278 find /etc\0 + + value ------------- Distribution ------------- count + -1 | 0 + 0 |@@@@@@@@@@@@@@@@@@@@ 251 + 1 | 0 + 2 |@ 8 + 4 | 5 + 8 |@ 10 + 16 |@ 10 + 32 |@ 10 + 64 |@ 9 + 128 |@ 11 + 256 |@ 14 + 512 |@@ 20 + 1024 |@ 10 + 2048 | 6 + 4096 |@ 7 + 8192 |@ 10 + 16384 |@ 16 + 32768 |@@ 21 + 65536 |@@ 28 + 131072 |@ 7 + 262144 |@ 14 + 524288 | 6 + 1048576 |@ 15 + 2097152 |@ 7 + 4194304 | 0 + + + 22282 tar cf /dev/null /etc\0 + + value ------------- Distribution ------------- count + -1 | 0 + 0 |@@@@@@@@@@ 397 + 1 | 0 + 2 | 8 + 4 | 14 + 8 | 16 + 16 |@ 24 + 32 |@ 29 + 64 |@@ 99 + 128 |@@ 73 + 256 |@@ 78 + 512 |@@@ 109 + 1024 |@@ 62 + 2048 |@@ 69 + 4096 |@@ 73 + 8192 |@@@ 113 + 16384 |@@ 81 + 32768 |@@@ 111 + 65536 |@@@ 108 + 131072 |@ 49 + 262144 |@ 33 + 524288 | 20 + 1048576 | 13 + 2097152 | 7 + 4194304 | 5 + 8388608 |@ 30 + 16777216 | 0 + |
