Severe performance hit over time with mmap usage

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Severe performance hit over time with mmap usage

Van Breuk
Dear devs,

I am testing Mergerfs to bundle two SSD drives, in order to handle a large database that was surpassing the single drive capacity. This database is run by a process that uses extensively large memory mapped files, on a high RAM (64 GB) Ubuntu server.

After reading in the Mergerfs documentation about FUSE performance issues when running mmap with older kernels, I upgraded my server to 4.5.4 kernel.

Still, the process starts fine from the Mergerfs mount point, with very reasonable resource usage, but after a few hours Mergerfs is staying over ~100% CPU usage, and the whole system lags noticeably.

Trapexit, developer for Mergerfs, suggested to bring it here since it could be essentially a FUSE issue, perhaps to do with caching. I will probably switch to another device management scheme like LVM, but if there's any details I can provide about my issue, please let me know.



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