[yocto] Suitable machine for yocto

[Mark Hatle]

On 9/10/17 11:14 AM, Alex Lennon wrote:
> 
> 
> On 10/09/2017 17:06, Mark Hatle wrote:
>> On 9/10/17 2:00 AM, Usman Haider wrote:
>>> Hi,
>>>
>>> Can someone please recommend some good machine for yocto environment and
>>> building sdks. I am interested in RAM, hard disk space, processor.
>> You want fast I/O, as much RAM and as many (fast) cores as you can afford.  I
>> don't think there is a single answer as what is 'best'.  It also depends on
>> which Yocto Project versions, and which layers you are using as to which
>> combination is best.
>>
>> I run builds on my laptop, 4-core/8-thread & SSD and 16 GB of ram from a few
>> years ago.  It's fast, but I wouldn't want to do all of my development on it.
>>
>> I've had 8-core/16-thread (32GB ram/standard disk), 16-core/32-thread (72GB
>> ram/SAS-3 RAID), 24-core/48-thread (64GB ram/SATA - software RAID), 72-core/144
>> thread (256 GB ram/hardware raid/SAS-3), and recently upgraded to
>> 96-core/192-thread (256 GB ram/hardware raid/SAS-3).
>>
>> I would not go below quad-core (8-thread) myself.  You can get a quad core, good
>> quality machine for $1000 or less these day.  If you move up to the larger
>> machines, you can even be able to get to a 24-core for less then $5000.  By the
>> time you get to 96-core and all of the googles you are likely talking $50000 or
>> more.
>>
>> By clock raid, the 24-core machine is the fastest..  While the 96-core monster
>> can do the builds the quickest.  But when you figure out cost/performance/etc..
>> the 24-core is probably the best performance per dollar, and with adequate RAM
>> (I'd say at least 64GB if not 128GB), and fast I/O you'll probably get the
>> lowest price for the best performance in that category.
>>
>> If you need sheer speed and price is no option, then the (4 CPU w/ 24 core each)
>> 96-core monster (or even better) is what you want to go with.  256GB ram would
>> be a minimum with that configuration (I'm not sure if more is actually helpful,
>> I rarely end up in swap -- but I go get into situations where more then 50% of
>> ram is used.)  With that many cores, disk I/O starts to become obvious.  So
>> faster the better... SSDs would be the fastest, but of course the most expensive.
>>
>> If your employer is paying for the machine, you may be able to get a better then
>> normal machine by explaining how much time a faster machine will save and how
>> comparing to your salary a machine is inexpensive.  (If you are a contractor or
>> student, that changes of course.)  :)
>>
>> So my point is really, figure out how much money you have to spend.  My rule of
>> thumb is roughly:
>>
>> 1) Buy as many cores as you can.  Try to get a CPU that has Hyperthreading or
>> equivalent to double the effective core count.  Fastest processing speed helps
>> in repetitive cases vs full system builds.
>>
>> So if the choice is a 24 core @ 2.2GHz vs 22 core @ 2.5, I'd probably go with
>> the 22-core.  While if it was 24 core @ 2.2GHz vs 8 core @ 4.2 GHz, I'd go with
>> the 24 core.
>>
>> 2) Try to get at least 1 GB of ram per thread (2 GB per core..)  You can cut
>> back on the ram (if necessary) once you hit 72 threads or so.   (72 threads
>> right now seems to cover most of the parallelization in a full system build.
>> There are points in the system where it can parallelize MUCH more, but they are
>> fairly rare.)
>>
>> 3) You need fast disks.  Software RAID works fine, but you likely need to buy at
>> least a couple of disk to boost performance.  SSDs are fast, but lots of builds
>> take space, so fast SATA or even better SAS drives are the best performance per
>> cost.
> 
> This brings to mind a related question I keep coming back to as to the 
> economics of a docker (or similar) image running a fast Yocto build in 
> the cloud.
> 
> i.e. set config params -> bring up server image on plaform A/B/C -> 
> perform build taking time X/Y/Z -> store output images -> bring down 
> server  == $ ?
> 
> I find myself asking what the optimal cost per-build would be using this 
> approach...

I helped someone do some very -preliminary- figured a few years ago.  The
processing was 'cheap', but between storage and network transfer costs.. it was
cheaper to buy a reasonable machine.. payback time was only a few months.

(cloud 'storage' is often very slow as well, because there are expectations of
migration and things like that.)

So as of a few years ago at least, the economics didn't factory the cloud -- yet.

--Mark

> Cheers,
> 
> Alex
>