Idea #21698
open
Research FUSE passthrough or splicing for FUSE v2
Updated by Peter Amstutz 12 months ago
From what I've been able to determine (documentation is limited) the way this works is that when a file open request happens, the FUSE daemon can say "this file is actually this other file over here" and return a file descriptor to the other file. Then the kernel essentially substitutes read/write operations on the FUSE file with operations on the real file.
https://github.com/libfuse/libfuse/pull/919
This doesn't really work for us except for situations where one block corresponds to one file.
Updated by Peter Amstutz 12 months ago
- Subject changed from Research FUSE passthrough for FUSE v2 to Research FUSE passthrough or splicing for FUSE v2
http://libfuse.github.io/doxygen/fuse__lowlevel_8h.html#a1242694fe0fb6e253a88b57795987302
Zero copy data transfer ("splicing") is possible when we write blocks to disk and read them back.
It isn't supported by python-llfuse, but is something to examine for "arv-client mount" -- this tells the kernel to go get the content to be returned by read() from a file descriptor instead of returning a buffer that has to be copied.