use of posix_fadvise/posix_fallocate

[Eric Blake]

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A complaint was recently raised on the cygwin list that the current cp
algorithm for regular files leads to disk fragmentation, since files are
only copied a block at a time.  In response, the cygwin developers
implemented both posix_fadvise and posix_fallocate.  Would it be worth
trying to write a gnulib module that provides substitutions for these
functions on lacking platforms (posix_fadvise being a no-op, and
posix_fallocate resolving to a call to ftruncate), then trying to improve
the copy algorithm in copy_reg() to inform the kernel that the source file
is read-once (POSIX_FADV_SEQUENTIAL, POSIX_FADV_NOREUSE), and that the
destination file is expected to occupy the same length as the source, so
that the resulting copy is potentially faster and less likely to be
fragmented on disk?

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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