Messages in this thread | | | Date | Thu, 20 Jan 2022 12:47:27 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: About perf tool set exclude_guest = 1 on guest environment |
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Em Thu, Jan 20, 2022 at 09:35:59PM +0800, Eric Lin escreveu: > On Wed, Jan 19, 2022 at 1:02 PM Namhyung Kim <namhyung@kernel.org> wrote: > > On Mon, Jan 17, 2022 at 8:05 PM Eric Lin <eric.lin@sifive.com> wrote: > > > Currently, I run the perf command 'perf record -e branches:u ls' and > > > 'perf record -e branches ls'. It will set exclude_guest = 1 as below: > > > > > > # perf record -e branches:u ls > > > # perf evlist -v > > > branches:u: .., exclude_kernel: 1, exclude_hv: 1,, exclude_guest: 1, .. > > > > > > # perf record -e branches ls > > > # perf evlist -v > > > branches: ..., exclude_guest: 1, ... > > > > > > As I understand it, set exclude_guest =1 will not include guest counting. > > > May I ask if I run the above commands as a guest user, should the > > > architecture implementation ignore this exclude_guest flags and still > > > make perf can count guest events in Linux kernel? > > > > So do you want to run the command in the host? > > Then you can use both 'H' and 'G' modifiers like > > > > # perf record -e branches:HG ls > > > > or (for user-mode only) > > > > # perf record -e branches:uHG ls > > > > Actually, I want to run the commands in the guest. > But when I run the commands "perf record -e branches:u ls" and "perf > record -e branches ls", it will set exclude_guet = 1. > According to the documentation[1] exclude_guest definition, it should > not count guest events. > So, if I run these commands as a guest user can I get the profile data? > > [1] https://man7.org/linux/man-pages/man2/perf_event_open.2.html
The tool shouldn't know that it is running in a guest, right?
And the kernel, running on a guest should exclude its guests if attr.exclude_guest is set, not itself and its non-guest userland.
So, before delving into how the kernel running on guest _actually_ handles attr.exclude_guest=1 behaves, what are the results you are getting from running perf on a guest?
Lemme see...
On a fedora:35 guest:
[root@fedora ~]# perf record ls anaconda-ks.cfg perf.data [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.014 MB perf.data (3 samples) ] [root@fedora ~]# perf evlist -v cpu-clock:pppH: type: 1, size: 128, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1 [root@fedora ~]#
IIRC there is some extra magic to allow 'cycles' to be seen on the guest, but apart from that it seems to work.
Eduardo, can you help us here?
- Arnaldo
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