On Sun, 23 Aug 2009, Ross Walker wrote:
O_DIRECT does just that, with or without barriers, it flushes on each
write, with an ever so slight delay to allow the queue to coalesce writes.
My bad O_DIRECT does NOT do that, it just goes direct to the driver bypassing
page cache. Allows for low latency IO and arbitrary IO sizes for throughput
(instead of page sized IO), but it doesn't enforce persistence.
Right. And Solaris does not support O_DIRECT. It does provide a
directio() function which requests similar functionality (as a hint)
but zfs does not support direct I/O. Linux O_DIRECT basically
requires an application re-write to use it and its precise function
tends to change across major kernel releases.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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