Hacker News new | ask | show | jobs
by scottlamb 70 days ago
I doubt they explicitly said "I'll run without huge pages, which is an important AWS configuration". They probably just forgot a step. And "someone at Amazon" describes a lot of people; multiply your mental probability tables accordingly.
1 comments
db48x 70 days ago
The number of people at Amazon is pretty much irrelevant; the org is going to ensure that someone is keeping an eye on kernel performance, but also that the work isn’t duplicative.

Surely they would be testing the configuration(s) that they use in production? They’re not running RDS without hugepages turned on, right?

link
scottlamb 70 days ago
> The number of people at Amazon is pretty much irrelevant; the org is going to ensure that someone is keeping an eye on kernel performance, but also that the work isn’t duplicative.

I'd guess they have dozens of people across say a Linux kernel team, a Graviton hardware integration team, an EC2 team, and a Amazon RDS for PostgreSQL team who might at one point or another run a benchmark like this. They probably coordinate to an extent, but not so much that only one person would ever run this test. So yes it is duplicative. And they're likely intending to test the configurations they use in production, yes, but people just make mistakes.

link
db48x 70 days ago
True; to err is human. But it is weird that they didn’t just fire up a standard RDS instance of one or more sizes and test those. After all, it’s already automated; two clicks on the website gets you a standard configuration and a couple more get you a 96c graviton cpu. I just wonder how the mistake happened.
link
menaerus 70 days ago
You're assuming that they ran the workload with huge-pages disabled unintentionally.
link
db48x 69 days ago
No… I’m assuming that they didn’t use the same automation that creates RDS clusters for actual customers. No doubt that automation configures the EC2 nodes sanely, with hugepages turned on. Leaving them turned off in this benchmark could have been accidental, but some accident of that kind was bound to happen as soon as the tests use any kind of setup that is different from what customers actually get.
link
menaerus 69 days ago
You're again assuming that having huge pages turned on always brings the net benefit, which it doesn't. I have at least one example where it didn't bring any observable benefit while at the same time it incurred extra code complexity, server administration overhead, and necessitated extra documentation.
link