[kwlug-disc] Meltown fix for Linux kernel

[Khalid Baheyeldin]

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-
> Retpoline-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
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