Perf kvm Could not open [], continuing without characters

Question

I am trying to control a guest OS with primary kvm. I recorded performance using the perf kvm record option, and generated a report using the perf kvm report. For recording and reporting, I used kallsyms guest OSs and modules, as described here .

The problem is that when I generate reports using the primary kvm report, a lot of the “common object” is unknown, because the primary kvm report cannot find characters. The following is the terminal output when I run the report.

root@computer1 :/# perf kvm --guest --guestmodules=modules report -i perf.data --force > waste Failed to open [ext4], continuing without symbols Failed to open [jbd2], continuing without symbols Failed to open [virtio_blk], continuing without symbols Failed to open [dm_mod], continuing without symbols Failed to open [virtio_pci], continuing without symbols Failed to open [virtio_ring], continuing without symbols 

And below is the part of the output that I redirected to a file where you can easily see the "unknowns".

 # To display the perf.data header info, please use --header/--header-only options. # # # Total Lost Samples: 0 # # Samples: 324K of event 'cycles' # Event count (approx.): 181799817277 # # Overhead Command Shared Object Symbol # ........ ....... ....................... .............................. # 1.30% :28468 [unknown] [u] 0x00007f3ae0262875 0.88% :28468 [unknown] [u] 0x00007f451f32d114 0.84% :28468 [unknown] [u] 0x00007f451f32d11d 0.49% :28468 [unknown] [u] 0x00007f451f32d118 0.45% :28468 [guest.kernel.kallsyms] [g] 0xffffffff8109aca3 0.43% :28468 [unknown] [u] 0x00007f3ae04c8891 0.42% :28468 [guest.kernel.kallsyms] [g] 0xffffffff810aa367 0.39% :28468 [unknown] [u] 0x000000343ca0a659 0.37% :28468 [unknown] [u] 0x00007f3ae04c8751 0.28% :28468 [unknown] [u] 0x000000343ca0b7c1 0.26% :28468 [unknown] [u] 0x000000343ca09223 0.25% :28468 [unknown] [u] 0x00007f451f32d116 0.23% :28468 [unknown] [u] 0x00007f3ae04c873e 0.21% :28468 [guest.kernel.kallsyms] [g] 0xffffffff8100c43f 0.20% :28468 [unknown] [u] 0x000000343ca09220 0.19% :28468 [unknown] [u] 0x00007f451f32d121 0.19% :28468 [guest.kernel.kallsyms] [g] 0xffffffff8100bb80 0.19% :28468 [guest.kernel.kallsyms] [g] 0xffffffff8150ffc2 

I read here that I need to install the dbgsym package, which I cannot understand for sure. (Note: I'm not new to Linux, but not an expert). I also tried to run the above command in the root folder, because I read somewhere that this could be an absolute path problem, etc., but to no avail.

I want to know how to deal with this problem of unknowns in the perf kvm report.

thanks

Answer 1

So, is RHEL your host and Ubuntu your guest?

As you already know, -dbgsym packages -dbgsym compiled with debugging symbols enabled. The ubuntu wiki has a page for retrieving packages -dbgsym.ddeb that you might find useful. There is also a kvm debug page, although it does not look too useful.