Kirk Strauser wrote:
Kris Kennaway wrote:
No, if it's reading in 16 byte units it will explain the terrible
performance.
No, it's actually doing 4096-byte reads. That was just an example of
what I meant.
I don't understand what you meant by "It's also doing a lot of lseek()s
to what is likely the current position anyway (example: seek to 0x00,
read 16 bytes, seek to 0x10, etc.)." then. Please show a typical part
of the ktrace output.
Kris
> Since I wrote that, though, I wrote a program to do
1,000,000 seeks to position 0, and it ran immeasurably fast. I'm
guessing that lseek() is optimized to not do anything if you ask it to
move to the position you're already at.
Any other thoughts? There definitely aren't any setbuf() calls, and no
matter what it still takes 100 times more kernel overhead on Linux than
FreeBSD. Speaking of which, I think my next experiment will be to try
the Linux binaries on FreeBSD and see if it behaves similarly.
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