Re: [gentoo-user] Better CPU for compiling with gcc

[Alec Ten Harmsel <alec@alectenharmsel.com>]

On 2015-11-10 14:07, Stanislav Nikolov wrote:
>
> On 11/10/2015 08:55 PM, Alan McKinnon wrote:
>> On 10/11/2015 20:37, Stanislav Nikolov wrote:
>>> On 11/10/2015 08:17 PM, Mick wrote:
>>>> On Tuesday 10 Nov 2015 17:47:08 Stanislav Nikolov wrote:
>>>>> Dear Gentoo users,
>>>>> I'm building a new PC. I have a budget of ~$550-$650.
>>>>>
>>>>> <snip>
>>>>>
>>>>> The most expensive Intel CPU is the skylake i7-6700k.
>>>>>
>>>>> Thanks
>>>>
>>
>> I can't help but think you are approaching this from the wrong perspective.
>>
>> Why exactly are you using compile times as your sole criterion? Are you
>> building a compile farm for Ubuntu? Running continuous integration tests
>> for LibreOffice [on a $600 budget in a cardboard box :-) ]?
>>
>> Or do you want emerge world to get it over with quicker?
>>
>> If the latter, you better rethink your priorities. In computing terms,
>> compilation is a rare event; launching apps is a common event; and
>> writing to the disk happens all the time. Optimize for the common case.

In addition, upgrades are something that can be done overnight, or 
really any time you are not using the machine.

>>
>> A CPU never works in isolation, it is always part of a much larger
>> system, like disks, RAM and all possible kinds of I/O. The best CPU on
>> the market plugged into a POS motherboard will perform on emerge world
>> like a piece of shit - it will follow the weakest link.

This; I have an i7-3930K, which has 6 physical cores at 3.8GHz. I also 
have 32GB of RAM and an SSD. There was a large speedup[1] moving 
portage's workdir from SSD to tmpfs. Compiling is a really balanced 
workload, stressing the disk (multiple small reads), memory, and CPU. 
For fast compilation, emphasize RAM first (compile in tmpfs if 
possible), then CPU, then disk. Like Alan said, though, you should 
really optimize for the average case on not worry about the speed of 
compiling stuff.

Alec

1. It was a long time ago so I don't remember the exact numbers, but my 
firefox compiling time went from ~15 minutes to ~10 minutes after 
switching from SSD to tmpfs for portage's workdir.