How Netflix uses Java • Hacker News Board

Re: How Netflix uses Java

#11

Post by groestl » Tue, Oct 10, 2023, 8:54 AM UTC

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

Because the memory / I/O is not the bottleneck anymore, and the CPU can now run optimally.

Re: How Netflix uses Java

#12

Post by Macha » Tue, Oct 10, 2023, 8:55 AM UTC

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

A somewhat common problem is to be limited by the throughput of CPU heavy tasks while the OS reports lower than expected CPU usage. A lot of companies/teams just kind of handwave it away as "hyperthreading is weird", and allocate more machines. Actual causes might be poor cache usage causing programs to wait on data to be loaded from memory, which depending on the CPU metrics you use, may not show as CPU busy time.

For companies at much smaller scale than netflix where employee time is relatively more costly than computer time, this might even be the right decision. So you might end up with 20 servers at 50% usage, but using 10 servers will take twice as long but still appear to be at 50% usage.

If the bottlenecks and overhead are reduced such that it's able to make more full use of the CPU, you might be able to reduce to e.g. 15 machines at 75% CPU usage. Consequently the increased CPU usage represents more efficient use of resources.

Re: How Netflix uses Java

#13

Post by groestl » Tue, Oct 10, 2023, 8:56 AM UTC

pyeri wrote: post #7

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

It's like hiring more workers to accomplish the exact same output as before. "See, I achieved 20% growth in my targets!", some recruiter will say!

No, it's like improving a form to minimize the need for follow-up questions to the customer, and now seeing your workers (the same you had before) processing 20% more forms instead of waiting for responses.

Re: How Netflix uses Java

#14

Post by yurishimo » Tue, Oct 10, 2023, 9:09 AM UTC

madaxe_again wrote: post #2

Ah, the way they break out artwork calls explains the weird behaviour I see with my U.K. Netflix account in Portugal - English titles, Portuguese posters, regardless of language preferences.

Yes because you’re being served the Portugal catalog. English is simply a localization setting that can be applied to any region.

Re: How Netflix uses Java

#15

Post by edpichler » Tue, Oct 10, 2023, 9:09 AM UTC

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

To free memory. Also, 20% increase is not 20% in total. It's 20% when you go from 10 to 12 cpu usage, or from 50 to 60, for instance.

Re: How Netflix uses Java

#16

Post by dewey » Tue, Oct 10, 2023, 9:10 AM UTC

madaxe_again wrote: post #2

Ah, the way they break out artwork calls explains the weird behaviour I see with my U.K. Netflix account in Portugal - English titles, Portuguese posters, regardless of language preferences.

How does the artwork explain that? Wouldn't they just need to call the artwork service with your current language preference instead of the default language of your current geolocation?

Re: How Netflix uses Java

#17

Post by inparen » Tue, Oct 10, 2023, 9:10 AM UTC

Spring Boot and Spring cloud for backend & graphql for the win. ;-)

Re: How Netflix uses Java

#18

Post by oldnet » Tue, Oct 10, 2023, 9:12 AM UTC

[flagged]

Re: How Netflix uses Java

#19

Post by moffkalast » Tue, Oct 10, 2023, 9:13 AM UTC

blackoil wrote: post #9

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

I think this is a 20% improved utilization of CPU, earlier app was memory-bound or/and GC was consuming CPU. Now app has 20% more CPU available. It should be doing correspondingly more work. This could definitely be written clearly.

> Bakker provided a retrospective of their JDK 17 upgrade that provided performance benefits, especially since they were running JDK 8 as recently as this year. Netflix observed a 20% increase of CPU usage

Seems like it's exactly that, OP cropped out the relevant bit where they list it having an overall performance benefit for that extra CPU time. Otherwise it could be assumed that it just hogs more CPU to get the same result.

Re: How Netflix uses Java

#20

Post by _the_inflator » Tue, Oct 10, 2023, 9:26 AM UTC

edpichler wrote: post #15

ValtteriL wrote: post #4

>Netflix observed a 20% increase of CPU usage on JDK 17 compared to JDK 8. This was mostly due to the improvements in the G1 garbage collector. Help me here, why do GC improvements cause CPU increase?

To free memory. Also, 20% increase is not 20% in total. It's 20% when you go from 10 to 12 cpu usage, or from 50 to 60, for instance.

Well done.

I always appreciate numbers and the differentiation between relative and absolute numbers in this case.

"We doubled our workforce in one week!" - CEO's first hire... ;)