Mkfile(8) is severely syscall limited on OS X

Re:Mkfile(8) is severely syscall limited on OS X by dom0 on Sunday February 12, 2017 @01:14PM (#13629629)

At just 60 MB/s it doesn't matter much (even 512 byte blocks would just be a little more than 100k syscalls / second). At a couple hundred MB/s it begins to matter, and with faster NVMe SSDs it's a legit issue.

This becomes a bigger issue if it's not a kernel-based, local FS, but something that does more work, I mentioned FUSE above. Since no read merging happens, small reads like 4k or 32k start to hurt earlier, especially if the FS is written in an interpreter. Some of these also mishandled small reads, incurring an additional penalty (I know because I fixed that in an implementation).

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Re:Mkfile(8) is severely syscall limited on OS X by gens on Sunday February 12, 2017 @01:30PM (#13629715)

No point in speculating. I showed you how. Go test it.

Even the fastest SSD is not even near the speed of /dev/zero. Easy to extrapolate any speed from those two points (minus the filesystem overhead (the thing we are talking about is the block layer)).

I'd be interested in a test of a FUSE based fs like ntfs. So if you have one, just run some tests. (don't forget to flush the cache)

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