Are threads bad? - was: Future of Pypy?

[Chris Angelico]

On Wed, Feb 25, 2015 at 4:46 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> Marcos Almeida Azevedo <marcos.al.azevedo at gmail.com>:
>
>> Synchronized methods in Java really makes programming life simpler.
>> But I think it is standard practice to avoid this if there is a
>> lighter alternative as synchronized methods are slow. Worse case I
>> used double checked locking.
>
> I have yet to see code whose performance suffers from too much locking.
> However, I have seen plenty of code that suffers from anomalies caused
> by incorrect locking.

Uhh, I have seen *heaps* of code whose performance suffers from too
much locking. At the coarsest and least intelligent level, a database
program that couldn't handle concurrency at all, so I wrote an
application-level semaphore that stopped two people from running it at
once. You want to use that program? Ask the other guy to close it.
THAT is a performance problem. And there are plenty of narrower cases,
where it ends up being a transactions-per-second throughput limiter.

ChrisA