MainMemory

The MainMemory project is intended to provide

• a framework for network servers of all sorts;
• some specific implementations of such servers.

The purpose of the MainMemory project is akin to SGI's State Threads Library (http://state-threads.sourceforge.net/). But MainMemory also aims to take full advantage of modern multi-core systems with large RAM sizes.

As the first application and testbed for the MainMemory framework the project provides almost complete implementation of the memcached protocol.

In the future it could also be used to implement any other protocol, for instance, redis. Or something completely different like HTTP, WebDAV, WebSocket protocols thus allowing to implement a caching HTTP server, proxy, storage platform, or a pub-sub system.

Status

The project has been slowly brewing as a personal research vehicle for some time already. A number of different approaches has been tried and abandoned. All this time it was run mostly against memslap and memtier benchmarks.

Now it has matured enough to consider it ready for experimental use by a wide audience. Hopefully in a short term it could be declared production ready as well.

Target Platforms

MainMemory is intended to run on x86/x86-64 boxes with Linux or any BSD flavor OS including macOS. The key requirement is the availability of either epoll or kqueue API in addition to the standard POSIX API.

However so far it has only been extensively tested on Linux and macOS. And on a single FreeBSD instance running on a VM. Therefore any portability reports and/or patches are welcome.

MainMemory includes a not-much-tested "generic architecture" port so there is a slim chance it will run on any non-x86 platform easily enough. But most likely it will take some extra work. In the future it is planed to have a native ARM port too.

Build

MainMemory relies on the venerable autotools suite to build. The build procedure is as follows:

> ./bootstrap
> ./configure <config-options>
> make

This produces few libraries and a binary file named 'maind' located in the 'src' subdirectory. The 'maind' file could be used as a replacement for your memcached.

Single-Threaded and Multi-Threaded Builds

MainMemory can be built in one of the two configurations:

• single-threaded
• or multi-threaded (SMP).

For the former option, run the configure script as follows:

> ./configure --disable-smp

For the later option, run the configure script as follows:

> ./configure --enable-smp

What Build to Use

The single-threaded version does not use the synchronization mechanisms of the multi-threaded version. Therefore it performs better (with higher throughput and smaller latency) until it hits the single-core execution limits.

As a rule of thumb if the required throughput of the server is less than about 100k requests per second then it might be beneficial to use the single-threaded build. Otherwise the multi-threaded build is preferred.

Development Builds

There are a few other configure options that might be useful during development. The following options enable collection and output (in somewhat cryptic format) of event loop and locking statistics:

> ./configure --enable-event-stats --enbale-lock-stats

The following options enable lots and lots of useless output (it was helpful however in the early days of the project):

> ./configure --enable-debug --enbale-trace

MacPorts Build

Builds on macOS are done using MacPorts. But the default MacPorts assembler may fail. If there are error messages like no such instruction then it is required to switch to the clang assembler.

First set the following environment variable:

 AS_INTEGRATED_ASSEMBLER=1

Then select any available MacPorts clang compiler, e.g.:

# sudo port select clang mp-clang-3.9

Note that it is still very possible to use gcc as the C compiler. It is just the assembler that needs to be borrowed from clang.