On Jan 5, 2007, at 11:10, Anton B. Rang wrote:
DIRECT IO is a set of performance optimisations to circumvent
shortcomings of a given filesystem.
Direct I/O as generally understood (i.e. not UFS-specific) is an
optimization which allows data to be transferred directly between
user data buffers and disk, without a memory-to-memory copy.
This isn't related to a particular file system.
true .. directio(3) is generally used in the context of *any* given
filesystem to advise it that an application buffer to system buffer
copy may get in the way or add additional overhead (particularly if
the filesystem buffer is doing additional copies.) You can also look
at it as a way of reducing more layers of indirection particularly if
I want the application overhead to be higher than the subsystem
overhead. Programmatically .. less is more.
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