From slitt at troubleshooters.com  Sat Aug  7 23:59:30 2021
From: slitt at troubleshooters.com (Steve Litt)
Date: Sat, 7 Aug 2021 16:59:30 -0400
Subject: Latest DNG software guide (20210807) now available
Message-ID: <20210807165930.64b8b091@mydesk.domain.cxm>

Hi all,

As you know, the people on the DNG Devuan mailing list are developing
documentation on how to make safe, resilient, maintainable and
efficient software.

The latest revision of this documentation can be downloaded, as a TGZ,
at 

http://troubleshooters.com/linux/presentations/golug_software_guide_20210807.tgz

This revision incorporates the input from the 8/4/2021 GoLUG meeting.
It can be downloaded with a simple wget command. Please make sure the
directory into which you downloaded the .tgz has no existing
golug_software_guide directory, or else moves and deletions won't be
respected.

Thanks,

SteveT

Steve Litt 
Spring 2021 featured book: Troubleshooting Techniques of the Successful
Technologist http://www.troubleshooters.com/techniques


From levonshe at yandex.com  Fri Aug 20 11:53:05 2021
From: levonshe at yandex.com (Lev Olshvang)
Date: Fri, 20 Aug 2021 11:53:05 +0300
Subject: How user space applications can take advantage of CPU features
Message-ID: <2447111629448161@mail.yandex.ru>

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From rabin at rabin.io  Fri Aug 27 16:48:31 2021
From: rabin at rabin.io (Rabin Yasharzadehe)
Date: Fri, 27 Aug 2021 16:48:31 +0300
Subject: How user space applications can take advantage of CPU features
In-Reply-To: <2447111629448161@mail.yandex.ru>
References: <2447111629448161@mail.yandex.ru>
Message-ID: <CABKuJED6=1aoym4p_ghxDYfMPv_JcRZvS4R743_EQ4U9y0AjXA@mail.gmail.com>

I'm not much of an expert, but the first thing that comes to mind is the
binary size and speed.
If you only need to implement the code once, and have a single optimized
version, the output will be smaller, and probably a bit faster.





--
Rabin


On Fri, 20 Aug 2021 at 11:54, Lev Olshvang <levonshe at yandex.com> wrote:

> Morning people of the Linux !
>
> Recently I came to a question I do not know the answer to although I am
> with Linux for >20 years,
>
> I am talking about the CPU architecture features likes SIMD, SSE, AES, ...
>  and related gcc CPU architecture switches
> -maes, -msse3, -msse4 -mrdrand are examples of such gcc switches.
>
> I know that OPENSSL queries  CPU features in run-time and then selects
> precompiled functions that takes advantage of a specific feature.
>
> I think the kernel does the same
>
> So I begin to think that such compiler switches are good only to C
> functions which are written in a very specific way to allow gcc to
> recognize graphic or crypto processing patterns and generate the assembly
> in order to utilize those assem;y extensions.
> Otherwise those switches does nothing good.
>
> Please enlighten me on the issue.
>
> Be Healthy,
> Lev
> _______________________________________________
> Linux-il mailing list
> Linux-il at cs.huji.ac.il
> http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
>
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From slitt at troubleshooters.com  Fri Aug 27 20:16:00 2021
From: slitt at troubleshooters.com (Steve Litt)
Date: Fri, 27 Aug 2021 13:16:00 -0400
Subject: How user space applications can take advantage of CPU features
In-Reply-To: <CABKuJED6=1aoym4p_ghxDYfMPv_JcRZvS4R743_EQ4U9y0AjXA@mail.gmail.com>
References: <2447111629448161@mail.yandex.ru>
 <CABKuJED6=1aoym4p_ghxDYfMPv_JcRZvS4R743_EQ4U9y0AjXA@mail.gmail.com>
Message-ID: <20210827131600.357f0140@mydesk.domain.cxm>

I'm less of an expert than either of you, but still have a piece of
advice:

If you use CPU specific code, I'd suggest all of the CPU specific code
be encapsulated within one or a very few objects, modules or data
structures with associated functions, so that if the unexpected happens
and you switch hardware, you can simply replace the object, module or
data structure with associated functions.

I think life would be hell if you had to search your whole codebase for
CPU specific code.

SteveT

Steve Litt 
Spring 2021 featured book: Troubleshooting Techniques of the Successful
Technologist http://www.troubleshooters.com/techniques


Rabin Yasharzadehe said on Fri, 27 Aug 2021 16:48:31 +0300

>I'm not much of an expert, but the first thing that comes to mind is
>the binary size and speed.
>If you only need to implement the code once, and have a single
>optimized version, the output will be smaller, and probably a bit
>faster.
>
>
>
>
>
>--
>Rabin
>
>
>On Fri, 20 Aug 2021 at 11:54, Lev Olshvang <levonshe at yandex.com> wrote:
>
>> Morning people of the Linux !
>>
>> Recently I came to a question I do not know the answer to although I
>> am with Linux for >20 years,
>>
>> I am talking about the CPU architecture features likes SIMD, SSE,
>> AES, ... and related gcc CPU architecture switches
>> -maes, -msse3, -msse4 -mrdrand are examples of such gcc switches.
>>
>> I know that OPENSSL queries  CPU features in run-time and then
>> selects precompiled functions that takes advantage of a specific
>> feature.
>>
>> I think the kernel does the same
>>
>> So I begin to think that such compiler switches are good only to C
>> functions which are written in a very specific way to allow gcc to
>> recognize graphic or crypto processing patterns and generate the
>> assembly in order to utilize those assem;y extensions.
>> Otherwise those switches does nothing good.
>>
>> Please enlighten me on the issue.
>>
>> Be Healthy,
>> Lev
>> _______________________________________________
>> Linux-il mailing list
>> Linux-il at cs.huji.ac.il
>> http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
>>