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One upside of code increasingly being written in languages that are predominantly single threaded like Python/JS is that these issues do not matter as much.

by dman 7y ago

anonuser123456 7y ago
If you want to exploit parallel execution for performance, not having parallelism is not a benefit.
- PeterCorless 7y ago
  We do parallelism across CPUs and nodes. We run single-threaded to get the most out of a CPU in a shared-nothing architecture. Many single-threaded apps aren't written to really take advantage of all a CPU has to offer. But there are also prices to pay to run multi-threaded; context switches, etc.
- wongarsu 7y ago
  Not having (thread-level) parallelism encourages designs with small, well defined interfaces where data crosses threads. In a typical NodeJS server setup with one load balancer and a number of node processes that don't know about each other you will experience fewer concurrency bugs and care less about NUMA than in the equivalent ASP.NET app (requests scheduled onto a thread pool, code can share resources at will). Of course sometimes "small interface" isn't really viable from a performance standpoint and you want a well-engineered multicore application with lots of shared data, and you just can't do that with JS or Python (or at least it's very hard). That's a good reason to choose a different language.
PeterCorless 7y ago
In the case of Scylla, we run on the Seastar engine, which runs single-threaded per core because it is very "greedy." Hence the CPU being pegged at 100%. It wasn't thrashing. We just squeezed everything we could out of it.
- dman 7y ago
  I think Scylla is a bit of an outlier in terms of software quality :) [I mean that as a compliment]
retrovm 7y ago
Being a good-enough CPU for terrible software is a bit of a tragic conclusion, in my view.
loeg 7y ago
ARM definitely doesn't win on single thread performance, so this is even worse for ARM. No?

One upside of code increasingly being written in languages that are predominantly single threaded like Python/JS is that these issues do not matter as much.

by dman 7y ago

One upside of code increasingly being written in languages that are predominantly single threaded like Python/JS is that these issues do not matter as much.

anonuser123456 7y ago

If you want to exploit parallel execution for performance, not having parallelism is not a benefit.

PeterCorless 7y ago
We do parallelism across CPUs and nodes. We run single-threaded to get the most out of a CPU in a shared-nothing architecture. Many single-threaded apps aren't written to really take advantage of all a CPU has to offer. But there are also prices to pay to run multi-threaded; context switches, etc.
wongarsu 7y ago
Not having (thread-level) parallelism encourages designs with small, well defined interfaces where data crosses threads. In a typical NodeJS server setup with one load balancer and a number of node processes that don't know about each other you will experience fewer concurrency bugs and care less about NUMA than in the equivalent ASP.NET app (requests scheduled onto a thread pool, code can share resources at will). Of course sometimes "small interface" isn't really viable from a performance standpoint and you want a well-engineered multicore application with lots of shared data, and you just can't do that with JS or Python (or at least it's very hard). That's a good reason to choose a different language.

PeterCorless 7y ago

In the case of Scylla, we run on the Seastar engine, which runs single-threaded per core because it is very "greedy." Hence the CPU being pegged at 100%. It wasn't thrashing. We just squeezed everything we could out of it.

dman 7y ago
I think Scylla is a bit of an outlier in terms of software quality :) [I mean that as a compliment]

retrovm 7y ago

Being a good-enough CPU for terrible software is a bit of a tragic conclusion, in my view.

loeg 7y ago

ARM definitely doesn't win on single thread performance, so this is even worse for ARM. No?