[Bug 1582181] Re: AArch64: slow cpuinfo due to redundant loop
Ubuntu Foundations Team Bug Bot
1582181 at bugs.launchpad.net
Mon May 16 12:34:18 UTC 2016
The attachment "AArch64-cpuinfo-Remove-redundant-cpu-caps-loop.patch"
seems to be a patch. If it isn't, please remove the "patch" flag from
the attachment, remove the "patch" tag, and if you are a member of the
~ubuntu-reviewers, unsubscribe the team.
[This is an automated message performed by a Launchpad user owned by
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** Tags added: patch
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https://bugs.launchpad.net/bugs/1582181
Title:
AArch64: slow cpuinfo due to redundant loop
Status in lshw package in Ubuntu:
New
Bug description:
lshw on AArch64 hardware is painfully slow.
This affects both lshw in current Ubuntu releases and vanilla upstream.
For a 48 core node, cpuinfo parsing added up to 30 seconds (8 lines
per core in /proc/cpuinfo add up to 384 lines to parse).
For a 96 core node, parsing took up to 5 minutes (!).
I think the problem was introduced by [1], and can be summarized as:
- CPU capabilities should be added only to the current CPU core,
and NOT to all previous CPU cores parsed.
My suggestion is dropping the loop in [1], thus calling the <addHint>
and <describeCapability> only for currentcpu.
I put together a small patch (basically removing the for loop in question)
at [2] (or see attachement), which should be applied on top of version
"02.16-2ubuntu1.3" from Ubuntu Trusty 14.04.
After applying the patch at [2], parsing for the above system (48 cores)
takes less than 1 second (instead of 30s), with the exact same results ...
[1]
https://github.com/lyonel/lshw/commit/beb89de5a3c10449fe73f1c77b2486d868e5bc9a
#diff-f4010714738fa4cdd5999499579da2b3R217
[2] http://paste.ubuntu.com/16456620/
# lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04
BR,
Alex
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