print runtime stats to the environment variable EMPER_STATS_FILE

See merge request !269

* Make all stats print methods accept a std::ostream as output.
* Move the printing of runtime component stats into Runtime::printStats.
* Use Runtime::printStats instead of Runtime::printLastRuntimeStats in
  ~Runtime, because we are already in a runtime which may differ from
  Runtime::currentRuntime.
* Write the stats in ~Runtime to a possible file passed in the
  environment variable EMPER_STATS_FILE

[sleep_strategy/Stats] remove old obsolete stats member

See merge request i4/manycore/emper!270

[Common.hpp] fix CACHE_LINE_EXCLUSIVE macro

See merge request i4/manycore/emper!268

[AbstractWorkStealingStats] actually use hint stats

See merge request i4/manycore/emper!267

[WakeupStrategy] fix the throttle algorithm for notifiaction from anywhere

Closes #26

See merge request i4/manycore/emper!266

Before 713c0f04 emper::sleep_strategy::Stats
had the actual stats member but with 713c0f04
WorkerStats are introduced which have the actual stats member but I
apparently forgot to remove the old now obsolete members.

Thanks clang for detecting this!

The macro did not replace symbol in __symbol_mem and always
created the literal symbol __symbol_mem which makes the
macro unusable in the same scope twice.

The throttle algorithm had the same problem like our sleep algorithms
where notifications from anywhere may race with a worker going to
sleep resulting in lost wakeups.
In the sleep strategy we prevent those races by preventing sleep attempts
when notifing from anywhere.
The throttle algorithm also does now exactly this. A notifier from anywhere
will now always set the WakeupStrategy state to notified.
If the state was previously pending this new approach does not differ from
the previous behavior and a sleeping worker will be notified.
If the state was waking the waking worker skips its sleep if it observes
the WakeupStrategy state as notified.

[log] improve timestamp scalability and increase LogBuffer size

See merge request i4/manycore/emper!265

std::localtime takes a global lock and is therefore not scalable and
inapplicable for analyzing timing sensible bugs.
Introduce a new option to add UTC timestamps. This allows on my system
to double the CPU load while using mmapped logging.

Also increase the LogBuffer size from 1MB to 1GB because I had some
crashes where a renewed buffer was still used.

[EchoServer] set SO_REUSEPORT on the listen socket

See merge request i4/manycore/emper!264

This is needed by emper-io-eval because apparently our startup/termination
times are shorter than the OS allows the rebinding of the same tcp tuple.

Also make all global variables static because they don't have to be exported.

[ConcurrentNetworkEchoTest] scale work with the available CPUs and log_level

See merge request i4/manycore/emper!262

[SimpleDiskAndNetworkTest] don't terminate the Runtime during the test

Closes #25

See merge request !261

The chosen amounts of echos take on my 16 core ryzen system ~5seconds.
This should hopefully reduce CI timeout where we are not sure if they are
bugs or legit timeouts. Furthermore this should reduce the amount of logs
we write and have to store after each CI run.

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 !255

introduce generic thread_local sleep strategy stats

See merge request !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 !253