Re: [lmi] perf

[Vadim Zeitlin]

On Mon, 28 Sep 2020 12:02:19 +0000 Greg Chicares <gchicares@sbcglobal.net> 
wrote:

GC> Perhaps chroots are just incompatible with 'perf'.

 I don't think so, a quick test using just chroot shows that it works fine.
However using chroot requires being root, of course, so it's not really a
solution. Maybe you could (temporarily) make /usr/sbin/chroot sgid root for
some group and add yourself to it and then run it (without forgetting
--userspec argument to also avoid being root in the chroot). This would be
definitely hacky, but I don't see why it wouldn't work.

GC> This works:
GC> 
GC> $perf record -e cpu-clock sleep 1                        
GC> [ perf record: Woken up 1 times to write data ]
GC> [ perf record: Captured and wrote 0.017 MB perf.data (3 samples) ]
GC> $perf report --stdio             
GC> 
GC> (the output is valid, even though it has little to say), but this fails:
GC> 
GC> $perf record -e cpu-clock -- schroot -c bullseye0 sleep 1
GC> [ perf record: Woken up 1 times to write data ]
GC> [ perf record: Captured and wrote 0.017 MB perf.data ]
GC> zsh: terminated  perf record -e cpu-clock -- schroot -c bullseye0 sleep 1

 Unfortunately, I have no idea what's going on here, perhaps I'm finally
going to need to install schroot to really understand it. But this
definitely doesn't seem normal or expected.

GC> My next step will be to compile lmi on the host. I haven't
GC> installed gcc there yet, but 'buster' has gcc-8.3.0-1, which
GC> should be good enough for now. For std::filesystem, we'll need
GC> gcc-10, which is in 'bullseye', and I'm sure it can't be too
GC> hard to install that in 'buster'.

 I'm afraid it's going to be difficult, i.e. installing the new package
will require upgrading so much that you will basically end up with a half
Buster/half Bullseye system, and mostly with Bullseye, I think.

 Regards,
VZ

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