linux-kernel - Re: [PATCH] perf symbols: Don't try to find a vmlinux file when looking for kernel modules

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Message-ID: <20200302200249.GA9761@krava>
Date:   Mon, 2 Mar 2020 21:02:49 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Kim Phillips <kim.phillips@....com>,
        Michael Petlan <mpetlan@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf symbols: Don't try to find a vmlinux file when
 looking for kernel modules

On Mon, Mar 02, 2020 at 04:10:07PM -0300, Arnaldo Carvalho de Melo wrote:
> The dso->kernel value is now set to everything that is in
> machine->kmaps, but that was being used to decide if vmlinux lookup is
> needed, which ended up making that lookup be made for kernel modules,
> that now have dso->kernel set, leading to these kinds of warnings when
> running on a machine with compressed kernel modules, like fedora:31:
>     
>   [root@...e ~]# perf record -F 10000 -a sleep 2
>   [ perf record: Woken up 1 times to write data ]
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   [ perf record: Captured and wrote 1.024 MB perf.data (1366 samples) ]
>   [root@...e ~]#
> 
> This happens when collecting the buildid, when we find samples for
> kernel modules, fix it by checking if the looked up DSO is a kernel
> module by other means.
> 
> Fixes: 02213cec64bb ("perf maps: Mark module DSOs with kernel type")

ok, I couldn't see that because kcore took over the modules,
for some reason you don't have it enabled on your system?

because I had to disable it manualy in the code.. I think
we should add some --no-kcore option for record

the fix is working for me:

Tested/Acked-by: Jiri Olsa <jolsa@...hat.com>

thanks,
jirka