
Membarrier system call performance and the future of Userspace RCU on Linux - readmodwrite
http://lttng.org/blog/2018/01/15/membarrier-system-call-performance-and-userspace-rcu/
======
MrBuddyCasino
tl;dr: apps are auto-linked to LTTng, which is a tracing framework. It
contains calls to the membarrier syscall, which in some cases waits until
every thread has context-switched at least once, which is kinda slow. New
kernel option solves this.

~~~
igravious
In order to debug the slow-down issue they use the command `perf trace
--duration 1 ./a.out' on where a.out is

    
    
      int main()
      {
      	return 0;
      }
    

and is built using `gcc -O2 -g -ldl -llttng-ust lttng-test.c'

Why is their tracing framework not able to trace itself? Is that a churlish
question?

~~~
viraptor
Lttng-ust is used primarily for static tracepoints. They needed a syscall
level visibility, so strace / perf trace is a better tool.

~~~
igravious
I see. Thank you!

