Re: arm64 qemu odd behavior

[Loic Dachary <loic@dachary.org>]

While compiling with 6 proc

$ cat /proc/cpuinfo
Processor	: AArch64 Processor rev 1 (aarch64)
processor	: 0
processor	: 1
processor	: 2
processor	: 3
processor	: 4
processor	: 5
Features	: fp asimd evtstrm
CPU implementer	: 0x50
CPU architecture: AArch64
CPU variant	: 0x0
CPU part	: 0x000
CPU revision	: 1

Hardware	: linux,dummy-virt

I noticed via htop that only 5 of them are in use during make -j6. Processor 4 is not used. I'm not sure how / if that can be repeated.

On 03/04/2016 23:18, Loic Dachary wrote:
> Hi Martin,
> 
> In your quest to understand why the arm64 qemu sometimes hangs when using as many processors as the host, maybe this will help. 
> 
> Today while watching an installation on an arm64 qemu machine, I noticed it was stuck in setting up fontconfig. So I logged in the machine, CPU was not busy, no IOwait either, a lot of free RAM. The host was also mostly idle. I straced the process and saw it moving. Unfortunately ( or maybe I was the cause of things starting to move on again ?) the font regeneration finished while I was observing and things seem to be going at a normal speed now. 
> 
> Note that there is almost a 2 hours gap between Setting up fontconfig and Regenerating fonts cache.
> 
> Maybe the pattern we're sometime seeing (i.e. all blocked, not even possible to ssh) is another case of the same issue ?
> 
> I'm starting to think we should bring this discussion to some arm64 mailing list or IRC channel but I don't know any.
> 
> 2016-04-03 19:17:34,858.858 DEBUG:teuthology.misc:Setting up libgdk-pixbuf2.0-0:arm64 (2.30.7-0ubuntu1.2) ...
> 2016-04-03 19:17:35,057.057 DEBUG:teuthology.misc:Setting up libthai-data (0.1.20-3) ...
> 2016-04-03 19:17:35,183.183 DEBUG:teuthology.misc:Setting up libdatrie1:arm64 (0.2.8-1) ...
> 2016-04-03 19:17:35,350.350 DEBUG:teuthology.misc:Setting up libthai0:arm64 (0.1.20-3) ...
> 2016-04-03 19:17:35,546.546 DEBUG:teuthology.misc:Setting up fontconfig (2.11.0-0ubuntu4.1) ...
> 2016-04-03 21:09:52,094.094 DEBUG:teuthology.misc:Regenerating fonts cache... done.
> 2016-04-03 21:09:52,136.136 DEBUG:teuthology.misc:Setting up libpango-1.0-0:arm64 (1.36.3-1ubuntu1.1) ...
> 2016-04-03 21:09:52,303.303 DEBUG:teuthology.misc:Setting up libgraphite2-3:arm64 (1.3.6-1ubuntu0.14.04.1) ...
> 2016-04-03 21:09:52,465.465 DEBUG:teuthology.misc:Setting up libharfbuzz0b:arm64 (0.9.27-1ubuntu1) ...
> 2016-04-03 21:09:52,641.641 DEBUG:teuthology.misc:Setting up libpangoft2-1.0-0:arm64 (1.36.3-1ubuntu1.1) ...
> 2016-04-03 21:09:52,806.806 DEBUG:teuthology.misc:Setting up libpangocairo-1.0-0:arm64 (1.36.3-1ubuntu1.1) ...
> 2016-04-03 21:09:52,971.971 DEBUG:teuthology.misc:Setting up libxcomposite1:arm64 (1:0.4.4-1) ...
> 
> Cheers
> 

-- 
Loïc Dachary, Artisan Logiciel Libre
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