Daniel Micay on Twitter: "@BRIAN_____ @johnregehr I have a lot of workloads where I get slightly better performance with it, but they could potentially be providing more performance by dropping it from the hardware and using the resources / complexity for something else like a larger L1 cache and TLB." / Twitter

This Tweet was deleted by the Tweet author. Learn more

Daniel Micay

@DanielMicay

Nov 2, 2018

Replying to

@BRIAN_____

I don't think SMT would be widespread if it wasn't such a great marketing tool. They use it to claim there are 2x the number of cores by talking about "logical cores" which is pretty much nonsense. The performance benefits are overrated and it can often impose a cost instead.

1

This Tweet was deleted by the Tweet author. Learn more

Replying to

and

I have a lot of workloads where I get slightly better performance with it, but they could potentially be providing more performance by dropping it from the hardware and using the resources / complexity for something else like a larger L1 cache and TLB.

6:53 PM · Nov 2, 2018Twitter Web Client

Replying to

and

I also have a lot of workloads where I don't get better performance, or where it hurts performance. The threads share an L1 cache and it's not necessarily a good thing to switch between them on stalls and have them pollute the cache used by the other thread. Can hurt latency too.

1

Replying to

and

There's also the issue that most applications will detect 2x the number of cores and spawn twice as many threads for worker pools. In jemalloc, it will result in having twice as many arenas, and to an extent that makes sense since the threads would block each other with locking.

1

Show replies

Conversation