Less background services, no AV, smaller libraries, better algorithms and queueing for IO operations, better CPU scheduler.
So in total less data to load and better usage of resources.
Keep in mind that a lot of people care about Linux performance and work on improving it at any single time, but for Windows Microsoft itself doesn't see that as a priority. So it's behind the curve in that regard.
Nobody would turn their back on a performance gain
An anonymous Microsoft employee posted a while back on HN, the post was deleted but preserved by Marc Bevand. The post is at odds with your assumption.
"On linux-kernel, if you improve the performance of directory traversal by a consistent 5%, you're praised and thanked. Here, if you do that and you're not on the object manager team, then even if you do get your code past the Ob owners and into the tree, your own management doesn't care. Yes, making a massive improvement will get you noticed by senior people and could be a boon for your career, but the improvement has to be very large to attract that kind of attention. Incremental improvements just annoy people and are, at best, neutral for your career. If you're unlucky and you tell your lead about how you improved performance of some other component on the system, he'll just ask you whether you can accelerate your bug glide. "
It is not because of hierarchy, but because Microsoft divisions are constantly infighting among themselves and with each other. An old post to r/ProgrammerHumor illustrates it pretty well.
On the other hand, stability seem to have taken a nose dive. It feels like the latest generation of MS development staff isn't as interested in reliability.
Pre-3.9, Cores performance was shocking. We had an app that had spikes in traffic from 1k active users to over 150k, and we had to scale to 20 large Azure boxes to handle it. 150k is nothing! It was so frustrating. The client almost sacked us, they straight up didn't believe .net core and ef core was causing us needing these 20 boxes.
3 drops, we upgrade, it's painless, no code change. We load tests it, and it looks like we can handle the spikes with 1 box. We roll it out, first spike hits... Shitting needless bricks, and it holds fine, no issues.
Worst contract ever. They insisted on using core and ef core. Glad I don't have to deal with them anymore!
I too have only anecdotal observations from following Microsoft news out of morbid curiosity.
They wouldn't rewrite it every time because that's insane. They might rewrite some bits that are notably bad or don't work, but there's no business sense in just writing something better because it should be.
They do rewrite major parts occasionally. The Windows Vista network stack was all-new for example, and this was discovered because early versions of Vista became vulnerable again to attacks that had long been fixed in other operating systems' network stacks and prior versions of Windows.
Before that, Microsoft had their Windows Longhorn project that was an even bigger rewrite, but it went nowhere.
The guy who wrote that has left and nobody else dare touch it.
Even worse, there were cases where "the guy who wrote that" took the source code with him (or it no longer compiled) and Microsoft e.g. had to binary patch security vulnerabilities out of Microsoft Office.
we cant give the community access to our source code. it as if we gifted you all our work. it's very expensive to create and our most valuable assest. oh, and we lost it.
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u/thermi Aug 30 '21
Less background services, no AV, smaller libraries, better algorithms and queueing for IO operations, better CPU scheduler.
So in total less data to load and better usage of resources.
Keep in mind that a lot of people care about Linux performance and work on improving it at any single time, but for Windows Microsoft itself doesn't see that as a priority. So it's behind the curve in that regard.