linux-kernel - Re: [PATCH] x86/AMD: Apply erratum 688 on machines without a BIOS fix

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Message-ID: <714acbaa1350bfe8927ccbea2425f4a9@openmailbox.org>
Date:   Mon, 24 Oct 2016 16:13:25 +0300
From:   sonofagun@...nmailbox.org
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, Nikos Barkas <levelwol@...il.com>
Subject: Re: [PATCH] x86/AMD: Apply erratum 688 on machines without a BIOS fix


> Sure, give me the exact command you're executing so that I can do it 
> here.
No command needed, just type:
sudo perf stat -a
and immediately exit with ctrl+C. That will give you a glimpse. See "% 
of all branches"
next open firefox, rerun the same command after firefox launches and 
immediately exit with ctrl+C
On that piece of crap I get branch-misses above 10% from boot without 
executing anything and perf does not like it so it displays it with red 
colour.
On my quad core kabini APU, in order to get 9% branch-misses I have to 
open 50 tabs on firefox. Something is terribly wrong here.

> Out of pure interest: do you remember how exactly you did reproduce 
> this
> issue?
Yes, using Ubuntu 16.04 will just crash everything! For example I had 
crashes with the software updater program. Moreover firefox would become 
unresponsive even with one tab.
Luckily initial tests of 16.10 seem promising as it is lighter and 
consumes 3~5% less RAM! Debian which was lighter was more responsive and 
had no crashes except an oops from adobe flash.
I believe that the bug is triggered by the unusually high branch-misses 
specific to this machine. After the fix, I got better OS and program 
responsiveness.