Hi Pavel, I'm looking at PosixSharedMemory again since I have to write a Master student proposal and I think this could be a good topic. I'm not really expert on SharedMemory, so I'm going to share what I have in mind, we can discuss about it, you could also co-supervise the student indirectly (though officially the supervisor has to be VUB staff).
Implementation-wise, I was thinking what could be interesting are: - Making PosixSharedMemory compatible with TaskIt so from you image you can create a SharedMemory buffer, spawn another image+VM and attach it to the shared memory to have multiple threads working on the shared section. - Add the #at:if:put: primitive, which write into the shared memory using compare and swap instruction for efficient thread-safe access. - Add on SharedMemory all the primitives to read/write native types to the buffer (int64, double, etc.) with CAS and non CAS instructions. - Maybe add APIs to read/write objects through Fuel to pass them by copy, though this looks difficult in some cases. - Implement a lock system or a semaphore system on top of the CAS - implement lock-free and lock-full algorithm using CAS and non CAS instructions (I think a first try would be parallelSort on a 1Gb buffer of int32 with 4 native threads) What do you think ? Do you have ideas ? Are you interested ? Do you thing having a student on this would be nice ? The master thesis proposal has to include a research question. I am not sure what other languages do regarding shared memory.It's not clear so far what the research question is. Best, On Mon, Feb 12, 2018 at 10:33 AM, Pavel Krivanek <pavel.kriva...@gmail.com> wrote: > Hi, > > among other less interesting things, I spent some time on existing > PosixSharedMemory project. It is a UFFI binding for the LibC methods > that provide support for the memory allocation between several > separate processes. I significantly improved the performance by > implementing the block access. Writing of 10MB byte array takes about > 1 millisecond, reading of it from other image took me about 4 > milliseconds. While serialization with Fuel is very fast, it opens > interesting possibilities. > To have a shared memory without synchronization tools is not very > useful so I wrote a basic UFFI interface for the POSIX named > semaphores. They are quite easy to use and work nicely with Pharo. The > VM can all wait on the semaphore or it can check the status of it > periodically in an image thread. It has two small disadvantages. It > requires to dynamically link the next library (pthread) and they must > be cleaned manually. I plan to look at System V alternative in future. > Now we should write a nice framework for inter-image communication on > top of it or/and adopt Seamless for it ;-) > > Cheers, > -- Pavel > > -- Clément Béra https://clementbera.github.io/ https://clementbera.wordpress.com/
