x265 HEVC Encoder

[tormento]

Originally Posted by excellentswordfight

But AFAIK the downclocking of AVX512 load have been improved since its introduction, and was less of an issue on consumer desktop models were frequency control is possible. But given what i've seen, i'm pretty sure that running it with AVX512 produces worse performance/watt.

It’s proven that AVX512 has more performance per watt. About downclocking: if you have a powerful heatsink AFAIK you can disable downclocking in bios.

[excellentswordfight]

Originally Posted by tormento

It’s proven that AVX512 has more performance per watt

Proven? For all systems with all software? Its pretty much a fact that has been worse for my cases; were enterprise-server hardware has been used. These systems are pretty strict in staying within it's power-specification, so when I get worse performance with AVX512 enabled, but it consumes the same amount of power (I have not messured the powerdraw this mind you, but im pretty sure thats the case given tempeture and freqency readings), then it means that it has a negative impact on performance/w. There are software were AVX512 instructions can do wonders, were it boosts performance by a great ammount, and there im sure that it has performance per watts benefits. But for x265, the performance gains of AVX512 are not that big, and at least with older generation hardware performance per watt has been lower, so unless you also increase power it have given me no gains.

About downclocking: if you have a powerful heatsink AFAIK you can disable downclocking in bios.

Yes, and thats also why i wrote:

"...less of an issue on consumer desktop models were frequency control is possible"

I have only tested AVX512 on Xeon/server hardware, and my old ice lake laptop. But as I said, I will try it on Sapphire Rapids, it will be interesting to see how it has been improved, cause first gen, both xeon and consumer (ice-lake) the downclocking rather big.

[nevcairiel]

AVX512 benefits start if you use it well and thoroughly, using it sparsely or inefficiently can cause more overhead then gain.
Blanket statements never make sense with complex optimizations and complex software. Test your own use-case on your own hardware.