Extremely Slow Read Speed from CFS with LZMA compression

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This topic contains 3 posts, has 3 voices, and was last updated by  rahul kumar 10 months, 1 week.

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  • Hi, I am getting between 15-20MB/sec read speed from CFS files created with LZMA and a maximum part size of 4.5GB (DVD5) (not sure if that’s relevant), just thought I’d mention it.

    Comparably, the same CFS file compressed with ZIP gets upwards of 100MB/sec read speed and in some cases, upwards of 300-350MB/sec when transfering to SSD. Clearly, zip decompresses fast enough that it doesn’t present a bottleneck.

    Is this normal behavior? Can CFS include options for fast decompression for LZMA?

    This is an issue for me because I’m trying to use CFS to store ROMs (Video game rips) that require frequent accessing, but due to the slow decompression or slow read speed, this causes hiccups, stalling, and other performance issues to occur for the emulator while it waits for a file inside the CFS to become fully decompressed and read.


    Joe Lowe
    Posts: 101

    LZMA is not going to be comparable to zip regarding performance. For your application I would suggest you stick with zip.

    If the CFS/CISO reader used multi-core decompression it would scale up a bit more for sequential IO, but zip would still be faster and scale better than LZMA.

    rahul kumar
    Posts: 1

    LZMA2 is faster for 4-threads, if you compress big file (more than 256 MB), so 7-Zip will be able to split it to blocks. LZMA2 was created for XZ format and it includes changes that are good for that stream compression format. Also LZMA2 is better than LZMA, if you compress already compressed data. LZMA decoder is simple. But PPMd decoder is complex. So now I don’t like the idea of PPMd / LZMA mixing.

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