Re: test-pthread-rwlock failure on Pop!_OS 22.04 LTS

[Bruno Haible]

Paul Eggert wrote:
> On my Pop_OS! laptop it's way slower than it was on any 
> of your measured VMs:
> 
> $ time ./test-pthread-rwlock
> Starting test_rwlock ...Alarm clock
> 
> real  10m0.002s
> user  90m18.341s
> sys   9m38.634s

Indeed, that's 5 times slower...

> Alternatively we could work around the performance bug, though that may 
> be too much work to justify.

It's more than a performance bug. If a program seems to work fine on
a system with 1 or 2 CPUs but consumes a time exponential in numCPUs,
due to writer starvation or reader starvation, that's a fundamental
problem. It's worse than the strstr O(n²) problem, because while
strstr takes a long run time for _larger_ inputs, the rwlock problem
makes the program take a long run time for the _same_ inputs.

Bruno