> They have basically forked their entire backend stack, starting from the OS and moving upwards.

Isn't this pretty common at the $XXX billion dollar tech companies like Google, Facebook, etc?

Most likely, yes, but that doesn't make it any less impressive

>Alibaba Runs Millions of Custom JVMs

>They have basically forked their entire backend stack, starting from the OS and moving upwards.

I doubt this being a cool thing. Sure, they are the second biggest IT employer in the country, and have excess resources for everything, but...

A thing about big dotcoms - architects there try to use off-the-shelf software for everything, even if the software is clearly unsuited for the task and its use will require hacks and massive re-engineering.

Putting efforts to use of off-the-shelf software without modifications and hacks greatly reduces all aspects of infrastructure support burden.

BUT, attempting to use of off-the-shelf software everywhere at all costs, that will of course give you problems. And the bigger your are, the worse this is. Read the article from a month ago how Alibaba got stuck with using MySQL for mission critical tasks, and how much efforts they put to "unhack" it

> "Read the article from a month ago how Alibaba got stuck with using MySQL for mission critical tasks, and how much efforts they put to "unhack" it"

Do you have a link for that?

Can you add a link to the article (Alibaba/mysql/etc ?!)

A video from Alibaba's mysql specialist, http://www.highload.ru/2015/abstracts/1915.html

I worked for Alipay, a subsidiary of Alibaba, around 2010. At that time, the tech stack was lagging behind compare to most silicon valley companies. But it was 7 years ago so things might changed since then.

It's certainly evolving.

Alibaba (and as well as other large online companies) had a huge leap during recent the Mobile Age as mobile phones makes online services more accessible to the public.

And government also enforced (impliedly) mobile carriers (China Unicom, China Mobile and China Telecom) to fueling this trend.

All this makes companies like Alibaba become very rich.

Plus, Alibaba's sites like taobao.com needs to handle tremendous amount of traffic in an average day, and even heavier traffic during promotion events like Nov 11 (Double 11) Day (It's like Black Friday[0]).

They had motive and resource to improve their system, and they opened some of those improvements already on GitHub[1]

[0] https://en.wikipedia.org/wiki/Black_Friday_%28shopping%29 [1] https://github.com/alibaba

> I am particularly interested in how much AliOS deviates from mainline Linux.

What could be the benefits of not using the mainline Linux for a stack like that?

If I were to guess, the benefits would result from making very "tight" optimizations to e.g. networking or scheduling that are specific to the workloads they deal with regularly.

Remember, Linux is designed to run on as many machine configurations and support as many workloads as possible. To achieve this, kernel devs sometimes cannot adopt the most optimized implementation because it may lead to unforeseen corner cases.

On the other hand, a company like Alibaba knows exactly what kind of machines and workloads they are dealing with, which means that they can make those optimizations and gain a slight performance boost relative to mainline Linux.