[kwlug-disc] Meltown fix for Linux kernel

[Khalid Baheyeldin]

And Ubuntu 16.04 users can't reboot the new kernel after applying the fixes.

Not a big deal if it is a desktop. If it is a dedicated server in a data
center, then it is downtime + support headaches.

https://news.slashdot.org/story/18/01/10/1634215/meltdown-and-spectre-patches-bricking-ubuntu-1604-computers

On Wed, Jan 10, 2018 at 9:24 AM, Khalid Baheyeldin <kb at 2bits.com> wrote:

> Wow, the differences are significant ...
>
> For a dedicated server, the fix for Meltdown is not really needed, since
> no one else is accessing RAM by exploiting the speculative execution.
>
> So I am thinking of pinning the kernel to what it is on those machines.
>
> But there are also headers, generic, ...etc.
>
> Anyone tried that?
>
>
>
> On Wed, Jan 10, 2018 at 8:31 AM, L.D. Paniak <ldpaniak at fourpisolutions.com
> > wrote:
>
>> Looks like you will see substantial performance impact for I/O-heavy
>> workloads (especially synthetic ones):
>>
>> https://www.phoronix.com/scan.php?page=news_item&px=KPTI-Ret
>> poline-Combined-Ubuntu
>>
>> The Apache server numbers are especially notable.
>>
>>
>>
>> On 01/09/2018 07:18 PM, doug moen wrote:
>>
>> According to what I read, the performance impact occurs if you are
>> hammering the kernel with a lot of system calls. Eg, a server that is
>> performing a lot of I/o.
>>
>> On Tuesday, 9 January 2018, Khalid Baheyeldin <kb at 2bits.com> wrote:
>>
>>> I just received the email for the meltdown patch for Ubuntu Linux.
>>>
>>> CVE-2017-5754
>>>
>>> There are two concerns:
>>>
>>> 1. Performance impact.
>>>
>>> 2. This comment in the email:
>>>
>>> "ATTENTION: Due to an unavoidable ABI change the kernel updates have
>>> been given a new version number, which requires you to recompile and
>>> reinstall all third party kernel modules you might have installed.
>>> Unless you manually uninstalled the standard kernel metapackages
>>> (e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
>>> linux-powerpc), a standard system upgrade will automatically perform
>>> this as well."
>>>
>>> Anyone updated to this fix yet?
>>> Any noticeable negative impact on performance?
>>>
>>> --
>>> Khalid M. Baheyeldin
>>> 2bits.com, Inc.
>>> Fast Reliable Drupal
>>> Drupal optimization, development, customization and consulting.
>>> Simplicity is prerequisite for reliability. --  Edsger W.Dijkstra
>>> Simplicity is the ultimate sophistication. --   Leonardo da Vinci
>>> For every complex problem, there is an answer that is clear, simple, and
>>> wrong." -- H.L. Mencken
>>>
>>
>>
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>
>
> --
> Khalid M. Baheyeldin
> 2bits.com, Inc.
> Fast Reliable Drupal
> Drupal optimization, development, customization and consulting.
> Simplicity is prerequisite for reliability. --  Edsger W.Dijkstra
> Simplicity is the ultimate sophistication. --   Leonardo da Vinci
> For every complex problem, there is an answer that is clear, simple, and
> wrong." -- H.L. Mencken
>



-- 
Khalid M. Baheyeldin
2bits.com, Inc.
Fast Reliable Drupal
Drupal optimization, development, customization and consulting.
Simplicity is prerequisite for reliability. --  Edsger W.Dijkstra
Simplicity is the ultimate sophistication. --   Leonardo da Vinci
For every complex problem, there is an answer that is clear, simple, and
wrong." -- H.L. Mencken
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