Hello,

Read this:


More about Lock-free algorithms..

I am a white arab, and i think i am smart, and now i will speak again
about Lock-free algorithms..

Here are the advantages of Lock-free algorithms:

Thread-killing Immunity: Any thread forcefully killed in the system
won't delay other threads.
Signal Immunity: The C and C++Standards prohibit signals or asynchronous interrupts from calling many system routines such as malloc. If the
interrupt calls malloc at the same time with an interrupted thread, that
could cause deadlock. With lock-free routines, there's no such problem
anymore: Threads can freely interleave execution.
Priority Inversion Immunity: Priority inversion occurs when a
low-priority thread holds a lock to a mutex needed by a high-priority
thread. Such tricky conflicts must be resolved by the OS kernel.
Wait-free and lock-free algorithms are immune to such problems.
Lock-free algorithms are good at convoy-avoidance.

But i have just thoughts more and i think that the most important things
to have is a bounded Lock-free LIFO stack and a bounded Lock-free FIFO
queue, since also i think that one of the most important is
convoy-avoidance, since also i think the fine-grained lock-based
Hashtables and Skiplists are still good at convoy-avoidance.

For the rest about Lock-free versus Lock , read my following post:

https://groups.google.com/forum/#!topic/comp.programming.threads/F_cF4ft1Qic


More about my new invention of a lock-free bounded LIFO stack algorithm..

I have just invented a lock-free bounded LIFO stack algorithm and i have
just made it work correctly in only one day, so i think version 1.04 is
stable now. I think that my new lock-free bounded LIFO stack algorithm
is really useful because it is not complicated , so it is easy to reason
about and it doesn't need ABA prevention and it doesn't need Hazard
pointers and it doesn't have false sharing, please look at its source
code inside LockfreeStackBounded.pas inside the zipfile, in my next
posts i will give you all the explanation of my new algorithm.

Lockfree bounded LIFO stack and FIFO queue were updated to version 1.04

You can read about them and download them from my website here:

https://sites.google.com/site/scalable68/lockfree-bounded-lifo-stack-and-fifo-queue


And I have just read the following IBM Research Report about Locks and convoying:

The convoy phenomenon

https://blog.acolyer.org/2019/07/01/the-convoy-phenomenon/

And i think that it is not so smart, because i am a white arab that is
smart like a genius , and i have invented a the Holy Grail of Locks that
is more powerful than the above, it is a scalable Fast Mutex
that is faster than the scalable MCS Lock, read about it in my
following thoughts:

I have invented a scalable algorithm that is a scalable fast Mutex that
is remarkable and that is the Holy Grail of scalable Locks, it has the following characteristics, read my following thoughts to understand:

About fair and unfair locking..

I have just read the following lead engineer at Amazon:

Highly contended and fair locking in Java

https://brooker.co.za/blog/2012/09/10/locking.html

So as you are noticing that you can use unfair locking that can have
starvation or fair locking that is slower than unfair locking.

I think that Microsoft synchronization objects like the Windows critical section uses unfair locking, but they still can have starvation.

But i think that this not the good way to do, because i am an inventor
and i have invented a scalable Fast Mutex that is much more powerful ,
because with my scalable Fast Mutex you are capable to tune the
"fairness" of the lock, and my Fast Mutex is capable of more than that,
read about it on my following thoughts:

More about research and software development..

I have just looked at the following new video:

Why is coding so hard...

https://www.youtube.com/watch?v=TAAXwrgd1U8

I am understanding this video, but i have to explain my work:

I am not like this techlead in the video above, because i am also an
"inventor" that has invented many scalable algorithms and there
implementions, i am also inventing effective abstractions, i give you an example:

Read the following of the senior research scientist that is called Dave
Dice:

Preemption tolerant MCS locks

https://blogs.oracle.com/dave/preemption-tolerant-mcs-locks

As you are noticing he is trying to invent a new lock that is preemption tolerant, but his lock lacks some important characteristics, this is why
i have just invented a new Fast Mutex that is adaptative and that is
much much better and i think mine is the "best", and i think you will
not find it anywhere, my new scalable Fast Mutex has the following characteristics:

1- Starvation-free
2- Tunable fairness
3- It keeps efficiently and very low its cache coherence traffic
4- Very good fast path performance
5- And it has a good preemption tolerance.
6- It is faster than scalable MCS lock
7- Not prone to convoying.

And about composability of lock-based systems now:

Design your systems to be composable. Among the more galling claims of
the detractors of lock-based systems is the notion that they are somehow uncomposable:

“Locks and condition variables do not support modular programming,”
reads one typically brazen claim, “building large programs by gluing
together smaller programs[:] locks make this impossible.”9 The claim, of course, is incorrect. For evidence one need only point at the
composition of lock-based systems such as databases and operating
systems into larger systems that remain entirely unaware of lower-level locking.

There are two ways to make lock-based systems completely composable, and
each has its own place. First (and most obviously), one can make locking entirely internal to the subsystem. For example, in concurrent operating systems, control never returns to user level with in-kernel locks held;
the locks used to implement the system itself are entirely behind the
system call interface that constitutes the interface to the system. More generally, this model can work whenever a crisp interface exists between software components: as long as control flow is never returned to the
caller with locks held, the subsystem will remain composable.

Second (and perhaps counterintuitively), one can achieve concurrency and composability by having no locks whatsoever. In this case, there must be
no global subsystem state—subsystem state must be captured in
per-instance state, and it must be up to consumers of the subsystem to
assure that they do not access their instance in parallel. By leaving
locking up to the client of the subsystem, the subsystem itself can be
used concurrently by different subsystems and in different contexts. A
concrete example of this is the AVL tree implementation used extensively
in the Solaris kernel. As with any balanced binary tree, the
implementation is sufficiently complex to merit componentization, but by
not having any global state, the implementation may be used concurrently
by disjoint subsystems—the only constraint is that manipulation of a
single AVL tree instance must be serialized.

Read more here:

https://queue.acm.org/detail.cfm?id=1454462

And you have to look here at our DelphiConcurrent and FreepascalConcurrent:

https://sites.google.com/site/scalable68/delphiconcurrent-and-freepascalconcurrent

Thank you,
Amine Moulay Ramdane.

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