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Re: CP Proposal - Benchmark + source code
From: |
Paul Eggert |
Subject: |
Re: CP Proposal - Benchmark + source code |
Date: |
Mon, 26 Sep 2005 10:18:53 -0700 |
User-agent: |
Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux) |
Thanks for the further measurements. It sounds like in the current
version of GNU/Linux, POSIX_FADV_NOREUSE | POSIX_FADV_SEQUENTIAL is
still much slower than O_DIRECT, even with kernel tweaking, so that is
an argument for having a new option for 'cp', 'mv', and 'install'. It
would be helpful to know, though, why the performance difference is so
great -- can you ask the kernel folks about that?
If we head this direction, one idea is to mimic the iflag and oflag
options that are already in 'dd'. Thus:
cp --iflag=direct --oflag=direct SOURCE DEST
would have the effect that you want. One could also specify other
combinations, e.g., --iflag='direct,noctty'. Perhaps it would also
make sense to have a combined --ioflag=direct option, for convenience.