Before 05dc56ed the two test cases testDiskAndNetwork, testIov
where combined in one function which was terminating the runtime after the client
closed its socketafter the test was done.
This was already broken before 05dc56ed but after the separation of the
two use cases the race between the Runtime terminating and the execution of
the last parts of the test-runner's alphaFiber became bigger.

When the Runtime terminates because the last worker running the testIoV
code has outstanding IO the test-runner's successSem is never notified.

disable throttle test in CI and add more debug messages.

See merge request i4/manycore/emper!263

[IoContext] replace fancy CQ locking with a mutex and CQ emptiness check

See merge request i4/manycore/emper!258

Also pass getWakeupCount the CallerEnvironment because this is the place
were we must change something to prevent lost wakeups when
notifying from anywhere.

[WakeupStrategy] introduce a new class to model our wakeup strategies

See merge request i4/manycore/emper!254

The macro uses std::aligned_storage to ensure the symbol
is properly cache line aligned and cache line sized.
This prevents cache line sharing with another symbol.

The actual symbol is initialized with the placement new operator
and for now must have a constructor without arguments.

[CI] enable IO in the now buster based CI

See merge request i4/manycore/emper!256

[tools/prepare-build-dir] fail if unknown meson option is set

See merge request i4/manycore/emper!257

* single io_uring
* pipe sleep strategy
* pipe sleep strategy without completer

* Use more emper io functions
* Split the separate test cases into two functions
* Use C++ arrays where sensible

Add new 'throttle' wakeup strategy inspired by the algorithm used
by zap, go and tokio. This tries to prevent a possible thundering herd
problem and reduce contention on the scheduler by only waking a single
worker at a time. It further ensures that the next worker is only notified
if the previous successfully found work.

Fix repeated ConcurrentNetworkEchoTest and SimpleNetworkTest

See merge request i4/manycore/emper!255

introduce generic thread_local sleep strategy stats

See merge request i4/manycore/emper!243

The tests may fail when repeated because the listener may bind to fast
to the tcp tuple again. This is fixed by using SO_REUSEPORT instead of SO_REUSEADDR.

TIL: SO_REUSEADDR is about address wildcards and SO_REUSEPORT allows
binding to the same tcp tuple.
https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ

Add a generic way to specify socket options when creating a listen socket
with tcp_listener.

[apps/qsort] implement quicksort benchmark used by kprotty

See merge request i4/manycore/emper!253

[lib/LinuxVersion] multiple fixes

See merge request i4/manycore/emper!252

* remove fancy but broken static LinuxVersion object.
  This means each usage of a EMPER_LINUX_* macro results in a syscall.
  But I think this is worth it when the result is a sound program.
  Users of those macros should store the result of the comparison anyway.
* fix that we skipped parsing the last part of a version string
* add a test for LinuxVersion
* IO_MUST_INVALIDATE_BROKEN_CHAIN can still be const

Deprecate IoContext submit broken chain logic

See merge request i4/manycore/emper!248

[apps/Coordinator] return SUCCESS when exiting successful not FAILURE

See merge request i4/manycore/emper!250

[io/tests] use our own ASSERT macro unaffected by NDEBUG

Closes #11

See merge request i4/manycore/emper!251

This allows use to remove the current hack that the test are always
build without NDEBUG regardless of the meson buildtype.

Which is fact fixes the failing io tests in release builds.
Because Future.hpp and Future.cpp see the same version of NDEBUG.

[Debug] implement logging to a memory-mapped log file

See merge request i4/manycore/emper!244

When setting the environment variable EMPER_LOG_FILE=<logfile> EMPER
will write its log messages to <logfile> instead of stderr.
This removes the need for the mutex protecting std::cerr as well as
multiple write calls to flush std:cerr.

To efficiently write log messages to the log file the algorithm uses
three memory 1MiB mapped views into <logfile> to store the log messages.
One buffer is active, one is new, and one is old.
The next buffer ensures that threads can write log messages even if the
active buffer would overflows.
The old buffer allows slower threads to still write safely while everyone
else uses the active buffer.
When a thread changes from the active buffer to the new buffer it
is responsible to renew the current old buffer and changing the semantic
of the buffers:

* active -> old
* next -> active
* old -> next

This buffer scheme allows wait-free logging.
But the approach is NOT sound because delayed thread may still use the
old buffer which gets renewed by the first thread touching the next buffer.
But the likeliness for this situation decreases with bigger sizes of the
buffers.

ATTENTION: Using SCHED_IDLE for the completer may break this likeliness
assumption.

Add new CI test job with mmaped log files.

This contains code cleanups
Suggested-By: Florian Schmaus <flow@cs.fau.de>

[PipeSleepStrategy] prevent the still present race to cqes with the completer

See merge request i4/manycore/emper!249

The previous race which I tried but in fact can not be fixed alone with
waitInflight flag is now described in the code comment in
PipeSleepStrategy::sleep().

To completely prevent the completer and the worker racing to the
new work notifications cqes we repurpose the cq_lock to ensure the
completer is always observing and honoring the waitInflight flag.

Also add an onNewWorkNotification callback to keep most sleep related
code and logic in PipeSleepStrategy.

[Make] use tidy make target instead of the meson generated clang-tidy target

See merge request i4/manycore/emper!247

[meson/liburing] switch to the official liburing wrap from meson wrapdb

See merge request i4/manycore/emper!246