Redis Windows, Performance Issues

Question

I am running redis on windows and I am having some performance issues. The machine is a Xeon E5 with 32GM RAM and SSD with HW-Raid with Windows Server 2012. There are some other processes running, but they are not critical and are idle most of the time.

I noticed performance problems and operations timeout very often, so I started "redis-cli --intrinsic-latency 100". The output shows that the max-latency goes up to 15000 microseconds, which is very slow I think.

I was also running a memory-profiler: The r/w-performance is not so good (5GB/sec) but I think this should not be the bottleneck. At the moment I have absolutly no idea what to try.

Can you give me some tipps how to find the performance problem?

Answer 1

There is no "fork" as in Linux in Windows. So when you dump your redis db, it can just "stop the world" in order to write on the disk "dump.rdb". Well, they did implement a "Copy-on-write" strategy that don't stop redis, it just copies values when dumping (the redis clients will still be able to get responses from redis). It is in their version log: https://github.com/MSOpenTech/Redis

There is a replacement for the UNIX fork() API that simulates the copy-on-write behavior using a memory mapped file.

This is the real bottleneck of redis in windows as it is an overhead and is more complex (bugs?). It is explained here:http://blogs.msdn.com/b/interoperability/archive/2012/04/26/here-s-to-the-first-release-from-ms-open-tech-redis-on-windows.aspx

As a result you could try running a redis on Linux to test if this is a performance issue of the windows port. Also, the more you write a dump.rdb, the bigger is the overhead (you can change the frequency or try disabling it completely for testing).

Finally, it could also be a network problem and you should check if it is not a network rule / hardware problem (not enough throughput! Bad cable or stuff, firewalls...). Are your redis clients on the same hardware machine?

Answer 2

I have been using a Windows port of Redis called "Memurai". They have a developer edition free of charge.

Now, in one of their blog they claim they have solved the fork() problem. See excerpt below.

Memurai performance seems good to me, even with persistence enabled (both RDB and AOF) although I have not run any specific test myself. There's another blog about Memurai perf in here.

It's worth giving it a try.

"Internally, Redis uses the fork() system call to perform asynchronous writes, but that’s not an option for Memurai because fork() doesn’t exist on Windows. Instead, Memurai uses Windows shared memory to implement a start-of-the-art version of fork() that’s finely tuned for performance and..."