linux-kernel - Re: [PATCH v2] perf record: fix priv level with branch sampling for paranoid=2

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Message-ID: <20190923141738.GB3617@redhat.com>
Date:   Mon, 23 Sep 2019 11:17:38 -0300
From:   Arnaldo Carvalho de Melo <acme@...hat.com>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
        jolsa@...hat.com, namhyung@...nel.org
Subject: Re: [PATCH v2] perf record: fix priv level with branch sampling for
 paranoid=2

Em Mon, Sep 23, 2019 at 11:03:45AM -0300, Arnaldo Carvalho de Melo escreveu:
> Thanks, tested added Jiri's Acked-by, applied, added this note:
> 
> Committer testing:
> 
> After aplying the patch we get:
> 
>   [acme@...co ~]$ perf record -b -e cycles date
>   WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
>   check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.
> 
>   Samples in kernel functions may not be resolved if a suitable vmlinux
>   file is not found in the buildid cache or in the vmlinux path.
> 
>   Samples in kernel modules won't be resolved at all.
> 
>   If some relocation was applied (e.g. kexec) symbols may be misresolved
>   even with a suitable vmlinux or kallsyms file.
> 
>   Mon 23 Sep 2019 11:00:59 AM -03
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.005 MB perf.data (14 samples) ]
>   [acme@...co ~]$ perf evlist -v
>   cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: ANY
>   [acme@...co ~]$
> 
> That warning about restricted kernel maps will be suppressed in a follow
> up patch, as perf_event_attr.exclude_kernel is set, i.e. no samples for
> the kernel will be taken and thus no need for those maps

Its there:

https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=c8b567c8a96a35acff746b1eef6f859e2a9fc195

- Arnaldo