Hi,It seems that my previous e-mail is not sent, properly. So, here is a link to the stackoverflow question:
https://stackoverflow.com/questions/60766026/wrong-perf-backtraces The perf is for Ubuntu 18.04 with the following "uname -a" output:Linux Ahmad-Laptop 5.0.0-37-generic #40~18.04.1-Ubuntu SMP Thu Nov 14 12:06:39 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux I also used a compiled Linux-5.4.7 kernel and its corresponding Perf tool.
Regards. On 2020-03-23 13:19, Jiri Olsa wrote:
On Mon, Mar 23, 2020 at 07:48:26AM +0430, ahmadkhorrami wrote:Here is a link to the detailed question at Stackoverflow: https://stackoverflow.com/questions/60766026/wrong-perf-backtraceshi, what perf version are you running? jirka I can copy it here, if needed. Thanks On 2020-03-23 05:04, Steven Rostedt wrote: On Mon, 23 Mar 2020 00:54:01 +0430 ahmadkhorrami <ahmadkhorrami@xxxxxxxx> wrote: Hi,I used "Perf" to extract call graphs in an evince benchmark. The commandused is as follows: sudo perf record -d --call-graph dwarf -c 10000 e mem_load_uops_retired.l3_miss:uppp /opt/evince-3.28.4/bin/evince I extracted the backtraces using "perf script" and found out that thereare many corrupted backtrace instances. Some contained repeated functioncalls, for example two consecutive gmallocn()s exactly at the sameoffsets. There are also some backtraces where the callers and callees donot match. Could you show some examples of the backtraces you mention?Note that that mappings are correct. In other words, each single line ofthe reported backtraces is correct (i.e., addresses match with functions). But is seems that there are some function calls in the middle, which are missed by "Perf". Strangely, in all runs (and also with different sampling frequencies) the problem occurs exactly at the same place. I am really confused and looking forward to any help. I can also send backtraces if needed. -- Steve
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