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Why aren't more people deploying FPGAs like this? I started looking into using FPGAs for distributed systems work about six years ago when I was building a dist

Why aren't more people deploying FPGAs like this? I started looking into using FPGAs for distributed systems work about six years ago when I was building a distributed database. Since then, about once a month I come across some problem that an FPGA could be useful for (i.e., enhance the performance enough that something otherwise infeasible becomes feasible). The devices themselves aren't that expensive (<$100) so why doesn't every server have one? Is there some hidden cost I'm not aware of (socket real estate, power consumption)? Or is it just a chicken-and-egg problem with not enough engineers asking for them because they don't know how they work because they're not more widely deployed?

rjsw 9y ago
There are plenty of PCI and PCIe cards available with an FPGA.
WorldMaker 9y ago
I would assume it's the chicken-and-egg problem. Why add a ~$100 component to a machine that might never be used? It's similar to how servers never had GPUs because that was a thing only consumers that play videogames need, right up until the point that a mixed combo of A) system on a chip manufacturers needed to always include a GPU for design simplicity, and B) GPUs were realized to be rather efficient generic math co-processors for a wider variety of problem domains than just "graphics" (because who needs graphics on a headless server?).
SomeStupidPoint 9y ago
Honestly? It's that I have no idea where to even buy a reasonable FPGA card with a high-speed interconnect so I could build my own Catapult-esque system. Something where I could buy a fully working card with standard networking FPGA blocks to build against, and have the FPGA mesh and PCI(e) connectors "just work" with minimal config. I've never moved off "well, that's cute" on demo boards because the market requires a lot of hardware customization to do anything neat (eg, MS designing their own for this). And, well, not to harp too much on the tooling... But the tooling is annoying. Workable, but annoying.
JoachimSchipper 9y ago
FPGAs are hard/expensive to program (including being very painful to debug), at least for most tasks - and few people are good at both FPGA and software development, so you may need different people to do the programming. New FPGA generations can require substantial re-work, at least for best performance. Many tasks would require kernel support (which is another "hard/expensive to program, and annoying to debug", although not nearly as bad). You need a deployment scenario where FPGAs beat GPUs (and CPUs) by enough to be worth that pain, but not by enough that someone already has a ready-made ASIC for you. I agree that one would expect to see more deployment of FPGA's naively, but not a lot.
- teemwerk 9y ago
  Yep, this right here. You really need a good reason to choose an FPGA. The inherent throughput and a lot of stuff is incredibly powerful, but the development is much more involved. To me anything sufficiently nontrivial always feels building a house with Lego.
- mmalone 9y ago
  This seems right, except that Microsoft has clearly developed a higher level language than VHDL / Verilog for writing "virtualized network functions" that compiles down to something they can flash onto an FPGA (they call it Flow Tables in the presentation). So there's a higher level language that's, presumably, more intuitive for "normal" engineers to work with. When a new FPGA comes out the compiler is re-written and high level code stays the same. Basically the same thing we do with CPUs. So they're not _inherently_ hard to program. SDN is common, and definitely a scenario where FPGAs outperform GPUs. Same for machine learning. (FWIW, Google uses ASICs for both of these use cases.) What we need is a high level language and access to FPGAs. I've been interested in business opportunities in this area, but it's hard to monetize. What's somewhat surprising is that the language bit hasn't been solved in the open source world either. My suspicion is that the reason an open source language like Flow Tables doesn't exist (AFAIK) is that there's not widespread access to FPGAs.
- Yizahi 9y ago
  One of the great benefits of FPGA compared to ASIC is that when you have some obscure low level bug appear you can just patch it on already sold devices, just like in software. You can also implement new features the same way, limited of course.
eli_gottlieb 9y ago
Maybe I think too recursively/iteratively, but I actually find it hard to think of problems where an FPGA is trivially valuable. How often am I just folding a function with fixed circuit-depth across a stream of values?

rjsw 9y ago

There are plenty of PCI and PCIe cards available with an FPGA.

WorldMaker 9y ago

I would assume it's the chicken-and-egg problem. Why add a ~$100 component to a machine that might never be used? It's similar to how servers never had GPUs because that was a thing only consumers that play videogames need, right up until the point that a mixed combo of A) system on a chip manufacturers needed to always include a GPU for design simplicity, and B) GPUs were realized to be rather efficient generic math co-processors for a wider variety of problem domains than just "graphics" (because who needs graphics on a headless server?).

SomeStupidPoint 9y ago

Honestly? It's that I have no idea where to even buy a reasonable FPGA card with a high-speed interconnect so I could build my own Catapult-esque system. Something where I could buy a fully working card with standard networking FPGA blocks to build against, and have the FPGA mesh and PCI(e) connectors "just work" with minimal config. I've never moved off "well, that's cute" on demo boards because the market requires a lot of hardware customization to do anything neat (eg, MS designing their own for this). And, well, not to harp too much on the tooling... But the tooling is annoying. Workable, but annoying.

JoachimSchipper 9y ago

FPGAs are hard/expensive to program (including being very painful to debug), at least for most tasks - and few people are good at both FPGA and software development, so you may need different people to do the programming. New FPGA generations can require substantial re-work, at least for best performance. Many tasks would require kernel support (which is another "hard/expensive to program, and annoying to debug", although not nearly as bad). You need a deployment scenario where FPGAs beat GPUs (and CPUs) by enough to be worth that pain, but not by enough that someone already has a ready-made ASIC for you. I agree that one would expect to see more deployment of FPGA's naively, but not a lot.

teemwerk 9y ago
Yep, this right here. You really need a good reason to choose an FPGA. The inherent throughput and a lot of stuff is incredibly powerful, but the development is much more involved. To me anything sufficiently nontrivial always feels building a house with Lego.
mmalone 9y ago
This seems right, except that Microsoft has clearly developed a higher level language than VHDL / Verilog for writing "virtualized network functions" that compiles down to something they can flash onto an FPGA (they call it Flow Tables in the presentation). So there's a higher level language that's, presumably, more intuitive for "normal" engineers to work with. When a new FPGA comes out the compiler is re-written and high level code stays the same. Basically the same thing we do with CPUs. So they're not _inherently_ hard to program. SDN is common, and definitely a scenario where FPGAs outperform GPUs. Same for machine learning. (FWIW, Google uses ASICs for both of these use cases.) What we need is a high level language and access to FPGAs. I've been interested in business opportunities in this area, but it's hard to monetize. What's somewhat surprising is that the language bit hasn't been solved in the open source world either. My suspicion is that the reason an open source language like Flow Tables doesn't exist (AFAIK) is that there's not widespread access to FPGAs.
Yizahi 9y ago
One of the great benefits of FPGA compared to ASIC is that when you have some obscure low level bug appear you can just patch it on already sold devices, just like in software. You can also implement new features the same way, limited of course.

eli_gottlieb 9y ago

Maybe I think too recursively/iteratively, but I actually find it hard to think of problems where an FPGA is trivially valuable. How often am I just folding a function with fixed circuit-depth across a stream of values?