Today's Bottleneck

Computers are always getting faster. From the perspective of the casual observer it may seem like every year all of the various specs keep going up, and systems are faster. [1] In truth, progress isn't uniform across all systems and subsystems, and thinking about this progression of technology gives us a chance to think about the constraints that developers [2] and other people who build technology face.

For most of the past year, I've used a single laptop, for all of my computing work, and while it's been great, in this time I lost touch with the comparative speed of systems. No great loss, but I found myself surprised to learn that all computers did not have the same speed: It wasn't until I started using other machines on a regular basis that I remembered that hardware could affect performance.

For most of the past decade, processors have been fast. While some processors are theoretically faster and some have other features like virtualization extensions and better multitasking capacities (i.e. hyperthreading and multi-core systems) the improvements have been incremental at best.

Memory (RAM) manages to mostly keep up with the processors, so there's no real bottleneck between RAM and the processor. Although RAM capacities are growing, at current volumes extra RAM just means services/systems that had to be distributed given RAM density can all run on one server. In general: "ho hum."

Disks are another story all together.

While disks got faster over this period, they didn't get much faster during this period, and so for a long time disks were the bottle neck in computing speed. To address this problem, a number of things changed:

• We designed systems for asynchronous operation.

Basically, folks spilled a lot of blood and energy to make sure that systems could continue to do work while waiting for the disk to reading or writing data. This involves using a lot of event loops, queuing systems, and so forth.

These systems are really cool, the only problem is that it means that we have to be smarter about some aspects of software design and deployment. This doesn't fix the tons of legacy sitting around, or the fact that a lot of tools and programmers are struggling to keep up.

• We started to build more distributed systems so that any individual spinning disk is responsible for writing/reading less data.

• We hacked disks themselves to get better performance.

  There are some ways you can eek out a bit of extra performance from spinning disks: namely RAID-10, hardware RAID controllers, and using smaller platters. RAID approaches use multiple drives (4) to provide simple redundancy and roughly double performance. Smaller platters require less movement of the disk arm, and you get a bit more out of the hardware.

  Now, with affordable solid state disks (SSDs,) all of these disk related speed problems are basically moot. So what are the next bottlenecks for computers and performance:

• Processors. It might be the case that processors are going to be the slow to develop bottleneck. There are a lot of expectations on processors these days: high speed, low power consumption, low temperature, high amount of parallelism (cores and hyperthreading.) But these expectations are necessarily conflicting.

  The main route to innovation is to make the processors themselves smaller, which does increase performance and helps control heat and power consumption, but there is a practical limit to the size of a processor.

  Also, no matter how fast you make the processor, it's irrelevant unless the software is capable of taking advantage of the feature.

• Software.

  We're still not great at building software with asynchronous components. "Non-blocking" systems do make it easier to have systems that work better with slower disks. Still, we don't have a lot of software that does a great job of using the parallelism of a processor, so it's possible to get some operations that are slow and will remain slow because a single threaded process must grind through a long task and can't share it.

• Network overhead.

  While I think better software is a huge problem, network throughput could be a huge issue. The internet endpoints (your connection) has gotten much faster in the past few years. That's a good thing, indeed, but there are a number of problems:

• Transfer speeds aren't keeping up with data growth or data storage, and if that trend continues, we're going to end up with a lot of data that only exists in one physical location, which leads to catastrophic data loss.

  I think we'll get back to a point where moving physical media around will begin to make sense. Again.

• Wireless data speeds and architectures (particularly 802.11x, but also wide area wireless,) have become ubiquitous, but aren't really sufficient for serious use. The fact that our homes, public places, and even offices (in some cases) aren't wired correctly to be able to provide opportunities to plug in will begin to hurt.

Thoughts? Other bottlenecks? Different reading of the history?