On Tue, Jun 13, 2017 at 11:04 PM, Namhyung Kim <namhy...@gmail.com> wrote: > Hello, > > On Wed, Jun 14, 2017 at 5:04 AM, Steven Rostedt <rost...@goodmis.org> wrote: >> On Tue, 13 Jun 2017 14:02:08 -0400 >> Will Hawkins <wh...@virginia.edu> wrote: >> >>> Thank you for pointing this out. I had been using -F for exactly the >>> reason that you mentioned. I failed to include it in the command that >>> I sent along. Very sorry for the confusion. Here is an updated version >>> of the command that I issued: >>> >>> >>> sudo ./trace-cmd record -e exceptions:page_fault_user -T --profile -l >>> handle_mm_fault -F ../one_page_play/page >>> >>> and I generated output like >>> >>> ./trace-cmd report --profile >>> >>> and I see the following (among some other output): >>> >>> Event: page_fault_user:0x7f094f7dd104 (1) >>> Event: page_fault_user:0x4000e0 (1) >>> Event: page_fault_user:0x7f094f7eae4a (1) >>> Event: page_fault_user:0x7f094f860d40 (1) >>> Event: page_fault_user:0x7f094f7db560 (1) >>> Event: page_fault_user:0x4040cb (1) >>> Event: page_fault_user:0x401825 (1) >>> Event: page_fault_user:0x401473 (1) >>> Event: page_fault_user:0x7f094f7e64c4 (1) >>> Event: page_fault_user:0x7f094f7f1212 (1) >>> >>> That output comes from under the task: page-<pid> heading, so it seems >>> like those faults are being attributed to the page task. >>> >>> This command seems to show something interesting: >>> >>> sudo ./trace-cmd record -e exceptions:page_fault_user -p >>> function_graph -g __do_fault -F ../one_page_play/page >>> >>> and the relevant output from >>> >>> ./trace-cmd report --profile >>> >>> is >>> >>> task: page-4032 >>> Event: func: __do_fault() (4) Total: 6685 Avg: 1671 Max: >>> 2398(ts:170150.060916) Min:855(ts:170150.054713) >>> Event: page_fault_user:0x7ffad3143d40 (1) >>> Event: page_fault_user:0x4000e0 (1) >>> Event: page_fault_user:0x401473 (1) >>> Event: page_fault_user:0x7ffad30c94c4 (1) >>> >>> This is closer to what I would expect. The first of the two 0x4... >>> addresses is the entry point and the second is the target. Basically, >>> that is exactly what I expect. The other two are the "suspicious" >>> entries. Neither matches the copy_user_enhanced_fast_string symbol >>> location and are not loaded in the binary (according to gdb). >> >> As you state below, there is faults recorded before the exec. Which is >> true with trace-cmd (not sure about perf). As trace-cmd does do some >> work after tracing is started and before the exec is called. > > When perf profiles a program started by the same command line, it > disables the events by default and enables them during exec. Please > see linux/tools/perf/util/evsel.c:perf_evsel__config(). > > Thanks, > Namhyung
Namhyung, I think that this answers a very important question! Thanks for chiming in! Will