Yocto Autobuilder: Latency Monitor and AB-INT - Meeting notes: July 1, 2021

Randy MacLeod

YP AB Intermittent failures meeting
July 1, 2021, 9 AM ET

Attendees: Alex, Richard, Saul, Randy


The autobuilder RCU hang is fixed, build greener.
ptest failures (some glibc-2.34) are the top problem now.

Add Michael Halstead, see questions below in section 4.

If anyone wants to help, we could use more eyes on the logs,
particularly the summary logs and understanding iostat #
when the dd test times out.

Plans for the week:


Richard: glibc upgrade, etc.

Alex: ?

Sakib: pub/non-release link upgrade, script clean-up.

Trevor: make job server test. Try it on YP AB!!! What type of build?

Tony: nothing this week for YP.

Saul: nothing this week for YP.

Randy: vacation!

Meeting Notes:

1. The qemu RCU hang has been fixed to not deadlock anymore!

It still hangs at times but this dramatically reduces the
AB failures.

2. Lots of ptest failures with
- tcl
- valgrind
especially with the upreved glibc-2.34.

3. YP AB INT # bugs reduced: down to ~ 47
Richard went through the list and closed ~ 10 bugs.
- RCU, LTP bugs closed.
- qemu ping bug remains

4. bitbake server timeout.

"Timeout while waiting for a reply from the bitbake server (60s)"

Randy mentioned that the bitbake server timeouts seen in the
Wind River build cluster have gone away after upgrading to
a newer version of docker.

Old: Docker Version: Docker version 18.09.4, build d14af54266
New: Docker Version: Docker version 20.10.7, build f0df350

Clearly the YP ABs aren't running in docker but what
about firmware and kernel tunings.


Is the BIOS/firmware kept up to date on most nodes?

It seems that we are running stock kernels which makes sense but
given that we don't have concerns about privacy since system access
is controlled and the nodes are being used to test open
source software, we might consider optimizing for performance
rather than security.

Alex pointed at: https://make-linux-fast-again.com/
Which just lists a set of kernel boot options:
noibrs noibpb nopti nospectre_v2 nospectre_v1 \
l1tf=off nospec_store_bypass_disable no_stf_barrier \
mds=off tsx=on tsx_async_abort=off mitigations=off

Can we enable some or all of these on a node to see what the
performance difference is?

5. io stalls

Richard said that it would make sense to write an ftrace utility
/ script to monitor io latency and we could install it with sudo
Ch^W mentioned ftrace on IRC.
Sakib and Randy will work on that but not for a week or two.

6. Switch the pub/non-release links from full log to summary.
The host data links on:
should include links to the summary data. I think we have room to
include both links like this:
0 1 2 3 (Full: 0 1 2 3 )

7. Qemu machine protocol debugging commands

Saul's patch is in.

8. System load: make, ninja jobs

Trevor has been busy with other work but has been playing with
kea and make -l: load average calculation

We're confirmed that this actually works on a build server and
for all versions of make in the cluster.

Randy may write to Paul Smith about the general problem we
are having.

9. iostat

The iostat output is in some of the AB logs:
for example:


search for "start: iostat"
it looks like the io sub-systems are 100% utilized but
we need more time, data and the summary script to be able to easily
make a general statement about AB INT issues and IO load and
to be able to identify what is typically generating the IO load.


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