Working on Linux?

[clSharp]

Do SharedBuffers work in Linux? Anyone successfully used it? As far as I understand it's based on named MemoryMaps, which are not supported in. NET Core under Linux.

Is there any alternative for shared memory with. NET Core under Linux?

[mkosina]

Got SharedArray to work on Linux with the following patches:

• in SharedBuffer.Open(), use MemoryMappedFile.CreateFromFile(), which is supported - and has the additional advantage of adding persistence to the buffer, something I needed
• in BufferWithLocks, replace usage of EventWaitHandle (which depends on named mutexes, also unsupported on Linux, though perhaps that has changed - see https://github.com/dotnet/coreclr/issues/3422) with a custom InterLocked.Exchange / spinWait locking

I only use SharedArray on Linux, so did the latter on SharedArray level only (via a secondary MMF of ints, which had the added benefit of fine-grained, per-cell locking), but could probably be adapted to BufferWithLocks in general.

I'll try to pull this together as a patch if there is interest, need to it dig out. Overall great library, using parts of it in a demanding server app (market data feed handler) without any issues - SharedArray for in-memory cache on Linux and CircularBuffer on Windows consumers to isolate GC-intolerant high bandwidth multicast consumption from rest of the client apps.

[mkosina]

May want to also check out https://github.com/AdaptiveConsulting/Aeron.NET - Martin Thomspon of LMAX Disruptor fame is involved.

[justinstenning]

@mkosina I would be interested in looking at integrating support for Linux.

I’m not sure how I feel about spin locks, but if there is no alternative for Linux then fair enough.

Would you be able to prepare a pull request or point to a repo that has these changes?

Thanks

[clSharp]

@mkosina Can you share experiences on when Linux flushes those mappings to disc? Will it flush if I delete the file before closing the map? Will it behave like memory maps backed by the page file and not write dirty pages as long as there is enough memory?

I need more than 1GB/s of shared memory bandwith. Any IO from those mappings is a serious problem for me.

[justinstenning]

My short investigation into this so far has found that the .NET core implementation on Linux only supports shared memory backed by files. I believe there is a memory only option within Linux, however this will require a custom implementation to support it.

[justinstenning]

As a note: cross-process mutex's are supported on Linux/POSIX with "Global\" prefix in name