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| Started by | Andi Kleen <andi@firstfloor.org> |
|---|---|
| First post | 2015-08-17 06:40 +0200 |
| Last post | 2015-08-17 20:30 +0200 |
| Articles | 3 — 2 participants |
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Announcing simple-pt -- a simple Processor Trace implementation for Linux Andi Kleen <andi@firstfloor.org> - 2015-08-17 06:40 +0200
Re: Announcing simple-pt -- a simple Processor Trace implementation for Linux Frederic Weisbecker <fweisbec@gmail.com> - 2015-08-17 15:10 +0200
Re: Announcing simple-pt -- a simple Processor Trace implementation for Linux Andi Kleen <andi@firstfloor.org> - 2015-08-17 20:30 +0200
| From | Andi Kleen <andi@firstfloor.org> |
|---|---|
| Date | 2015-08-17 06:40 +0200 |
| Subject | Announcing simple-pt -- a simple Processor Trace implementation for Linux |
| Message-ID | <pYkng-55o-25@gated-at.bofh.it> |
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 has an integrated PT implementation in perf
(see https://lwn.net/Articles/648154/).
simple-pt is an alternative implementation. It has many disadvantages over the perf PT
implementation, such as:
- needs to run as root
- no long term tracing or sampling with interrupts
- no support for interactive debugging (use gdb 7.10 on perf for that)
- no support for histograms
- somewhat experimental
- not as well supported as perf
On the positive side simple-pt is:
- simple
- standalone. No kernel changes needed. Could be ported to older kernels or other operating systems
- easy to modify and experiment with
- more ftrace like decoding tool
- support for kprobes based triggers
- modular “unix style” design with simple tools that do only one thing each
- BSD licensed
Example output:
% sptcmd -c tcall taskset -c 0 ./tcall
cpu 0 offset 1027688, 1003 KB, writing to ptout.0
...
Wrote sideband to ptout.sideband
% sptdecode --sideband ptout.sideband --pt ptout.0 | less
TIME DELTA INSNs OPERATION
frequency 32
0 [+0] [+ 1] _dl_aux_init+436
[+ 6] __libc_start_main+455 -> _dl_discover_osversion
...
[+ 13] __libc_start_main+446 -> main
[+ 9] main+22 -> f1
[+ 4] f1+9 -> f2
[+ 2] f1+19 -> f2
[+ 5] main+22 -> f1
[+ 4] f1+9 -> f2
[+ 2] f1+19 -> f2
[+ 5] main+22 -> f1
...
Available from https://github.com/andikleen/simple-pt
--
ak@linux.intel.com -- Speaking for myself only.
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| From | Frederic Weisbecker <fweisbec@gmail.com> |
|---|---|
| Date | 2015-08-17 15:10 +0200 |
| Subject | Re: Announcing simple-pt -- a simple Processor Trace implementation for Linux |
| Message-ID | <pYskP-8di-25@gated-at.bofh.it> |
| In reply to | #1208363 |
2015-08-17 6:31 GMT+02:00 Andi Kleen <andi@firstfloor.org>: > > 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 has an integrated PT implementation in perf > (see https://lwn.net/Articles/648154/). > simple-pt is an alternative implementation. It has many disadvantages over the perf PT > implementation, such as: > - needs to run as root > - no long term tracing or sampling with interrupts > - no support for interactive debugging (use gdb 7.10 on perf for that) > - no support for histograms > - somewhat experimental > - not as well supported as perf > > On the positive side simple-pt is: > - simple > - standalone. No kernel changes needed. Could be ported to older kernels or other operating systems > - easy to modify and experiment with > - more ftrace like decoding tool > - support for kprobes based triggers > - modular “unix style” design with simple tools that do only one thing each > - BSD licensed > > Example output: > > > % sptcmd -c tcall taskset -c 0 ./tcall > cpu 0 offset 1027688, 1003 KB, writing to ptout.0 > ... > Wrote sideband to ptout.sideband > % sptdecode --sideband ptout.sideband --pt ptout.0 | less > TIME DELTA INSNs OPERATION > frequency 32 > 0 [+0] [+ 1] _dl_aux_init+436 > [+ 6] __libc_start_main+455 -> _dl_discover_osversion > ... > [+ 13] __libc_start_main+446 -> main > [+ 9] main+22 -> f1 > [+ 4] f1+9 -> f2 > [+ 2] f1+19 -> f2 > [+ 5] main+22 -> f1 > [+ 4] f1+9 -> f2 > [+ 2] f1+19 -> f2 > [+ 5] main+22 -> f1 Nice. So I guess +x is the address offset. How hard would it be to translate to file lines? Thanks. > ... > > Available from https://github.com/andikleen/simple-pt > > -- > ak@linux.intel.com -- Speaking for myself only. > -- > To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Andi Kleen <andi@firstfloor.org> |
|---|---|
| Date | 2015-08-17 20:30 +0200 |
| Subject | Re: Announcing simple-pt -- a simple Processor Trace implementation for Linux |
| Message-ID | <pYxkt-6Ss-3@gated-at.bofh.it> |
| In reply to | #1208575 |
> > % sptdecode --sideband ptout.sideband --pt ptout.0 | less > > TIME DELTA INSNs OPERATION > > frequency 32 > > 0 [+0] [+ 1] _dl_aux_init+436 > > [+ 6] __libc_start_main+455 -> _dl_discover_osversion > > ... > > [+ 13] __libc_start_main+446 -> main > > [+ 9] main+22 -> f1 > > [+ 4] f1+9 -> f2 > > [+ 2] f1+19 -> f2 > > [+ 5] main+22 -> f1 > > [+ 4] f1+9 -> f2 > > [+ 2] f1+19 -> f2 > > [+ 5] main+22 -> f1 > > Nice. So I guess +x is the address offset. How hard would it be to > translate to file lines? Yes it's the address offset. Translating to lines wouldn't be too hard, just needs to be implemented with a dwarf reader. BTW the PT trace has all branches, just not the calls, but it's more difficult to display them all in a nice way. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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