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Comment by pclmulqdq | Hacker News Reader

QAT is awesome, and flips the script on the notion of core count primacy. In many servers, QAT when properly used will save several CPU cores, since cores spend a lot of time compressing and encrypting stuff. However, the software layer has always been Intel's weakness, and I'm not entirely sure they got this one right.

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Intel's software has always been pretty good for me. You're complaining about the need for a driver, right? That seems reasonable, more like a weakness of cloud computing that it takes so long for clouds to expose the real capabilities of the hardware. It's a win for those who can (re)master dedicated machines and attendant Linux sysadmin issues.

I think the driver and software resources have been very messy. There are different versions, hardware revisions, different QAT generations... and at first glance is very confusing to know how you can run certain accelerations.

For example, the Zstandard plugin has this requirements:

  Hardware Requirements
    Intel® 4xxx (Intel® QuickAssist Technology Gen 4)
    Software Requirements
  ZSTD* library of version 1.5.4+
    Intel® QAT Driver for Linux* Hardware v2.0

What's Gen 4? (I later found that means '4th Generation Intel® Xeon® Scalable Processors'. But not any Gen4, you have to find one with QAT included, and the product matrix is huge.)

What's the v2.0 of the hardware? (I'm not completely sure about that)

Does it automatically accelerate zlib and openssllib calls, or do you have to patch them? (I think you have to patch them)

I think they're stabilizing the API from now on, but it's not as simple as buying a CPU or one of the older PCIe cards, and loading the driver.

Yes OK, I don't have direct experience with QAT and wasn't really counting getting the right hardware in the software experience. Their product matrix is very confusing.

This is about Intel's drivers, which are usually buggy and subpar if you can figure out which ones to use (without contacting your FAE - not all of us have one of those), and the fact that they don't expose their hardware to you in a meaningful fashion. You have to access it through the programming models they want you to use, which usually involve a lot of overhead.

What does exposed in a meaningful fashion mean here? Their drivers all seem to be open source, so the hardware is exposed directly.

Out of curiosity, what are some use cases? The only one I'm even remotely familiar with is https encryption offloading.

This sounds like it would be great for filesystem compression (e.g. ZFS).

Is this available in any public cloud?

AWS has it.

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