Packing functions in memory such that caller/callee are more likely to be on same cache line / same page. (Surprising to see the "same cache line" part actually happens 5% of the time; the ITLB improvements make a lot more intuitive sense). Do this using callgraph information collected continuously from production machines.
Then use same mechanism for keeping the very hottest code in huge pages. Can't do this universally, due to the tiny number of hugepage I-TLB entries.
5-10% improvements across a selection of Facebook's services.
(Excluding FreeBSD on their CDN servers, of course). Asked in the context of Gregg being an ex-Solaris hacker.
It's very easy for people to underestimate how big the cumulative effect from 20 years of even slightly faster improvements ends up being. E.g. were there any major enhancements to the Illumos TCP stack in this decade? If ther were, it's at least not obvious. Or (since I dug this post out due to a "Why would people run Linux instead of OpenBSD" discussion), anyone wanting to run a major Internet service on OpenBSD would probably need to hire 1-2 fulltime hackers to modernize the TCP implementation.
That's just the bit of operating systems I'm familiar with. But hard to believe it would somehow be a unique problem area./p>
An investigation of HTTP middleboxes all over the internet. How do they behave, and how do you fool them into doing things they weren't meant to do.
The Gamecube had a GPU with some programmable parts, rather than being purely fixed-function. For Dolphin to emulate that, they need to compile the Gamecube GPU programs to modern GPU shaders. But this compilation takes time, and they don't know the set of needed shaders up front (it's fully dynamic). How do you solve that?
> But what if we don't have to rely on specialized shaders? The crazy idea was born to emulate the rendering pipeline itself with an interpreter that runs directly on the GPU as a set of monsterous flexible shaders.
The great thing about Dolphin updates is that they don't just explain what a new feature is; they explain what other solutions have been tried or proposed, and why those solutions don't actually work.