Modern Intel Core CPUs (5th and 6th generation) have a Intel Processor Trace (PT) feature to trace branch execution with low overhead. This is useful for performance analysis and debugging.<\/p>\n

simple-pt is a simple standalone driver and decoder tool to implement PT on Linux.<\/p>\n

Starting with Linux 4.1 Linux already has a integrated PT implementation in perf (see https:\/\/lwn.net\/Articles\/648154\/<\/a> ). simple-pt is an alternative implementation. It has many disadvantages over the perf PT implementation, such as:
\n– needs to run as root
\n– no long term tracing or sampling with interrupts
\n– no support for interactive debugging (use gdb 7.10 on perf for that)
\n– no support for histograms
\n– somewhat experimental
\n– not as well supported as perf<\/p>\n

On the positive side simple-pt is:
\n– simple
\n– standalone. No kernel changes needed. Could be ported to older kernels or other operating systems
\n– easy to modify and experiment with
\n– more ftrace like decoding tool
\n– support for kprobes based triggers
\n– modular “unix style” design with simple tools that do only one thing each
\n– BSD licensed<\/p>\n

Example output:<\/p>\n

\r\n\r\n        % sptcmd  -c tcall taskset -c 0 .\/tcall\r\n        cpu   0 offset 1027688,  1003 KB, writing to ptout.0\r\n        ...\r\n        Wrote sideband to ptout.sideband\r\n        % sptdecode --sideband ptout.sideband --pt ptout.0 | less\r\n        TIME      DELTA  INSNs   OPERATION\r\n        frequency 32\r\n        0        [+0]     [+   1] _dl_aux_init+436\r\n                          [+   6] __libc_start_main+455 -> _dl_discover_osversion\r\n        ...\r\n                          [+  13] __libc_start_main+446 -> main\r\n                          [+   9]     main+22 -> f1\r\n                          [+   4]             f1+9 -> f2\r\n                          [+   2]             f1+19 -> f2\r\n                          [+   5]     main+22 -> f1\r\n                          [+   4]             f1+9 -> f2\r\n                          [+   2]             f1+19 -> f2\r\n                          [+   5]     main+22 -> f1\r\n        ...\r\n<\/code>\r\n<\/pre>\n
Available from https:\/\/github.com\/andikleen\/simple-pt<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
Modern Intel Core CPUs (5th and 6th generation) have a Intel Processor Trace (PT) feature to trace branch execution with low overhead. This is useful for performance analysis and debugging. simple-pt is a simple standalone driver and decoder tool to implement PT on Linux. Starting with Linux 4.1 Linux already has a integrated PT implementation […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[7,17],"tags":[],"_links":{"self":[{"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/posts\/344"}],"collection":[{"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/comments?post=344"}],"version-history":[{"count":10,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/posts\/344\/revisions"}],"predecessor-version":[{"id":354,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/posts\/344\/revisions\/354"}],"wp:attachment":[{"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/media?parent=344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/categories?post=344"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/halobates.de\/blog\/wp-json\/wp\/v2\/tags?post=344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}