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DragonFly kernel List (threaded) for 2005-12
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Re: Plans for 1.5

From: Jason <jason@xxxxxxxxxxxx>
Date: Sat, 17 Dec 2005 18:28:53 -0600

Matthew Dillon wrote:
			    STAGE 2 - I/O Subsystem
			    Starting early February!

What are your thoughts on also adding a new flag to madvise to prefault pages, so as to avoid faults through the VM system?

Perhaps a flag named MADV_PREFAULT, or to be consistent with MADV_WILLNEED, MADV_NEEDNOW. Of course, such a call would be limited to a maximum size per call, which is queryable, etc.

As I recall, this is one of your main points for using buffered read/write calls instead of mmap. This could be even more significant with faults causing page-ins from cross-system boundaries.

Also, how about extending sendfile to behave as a general copyfile, or simply adding a general copyfile syscall?

With a framework like CCMS it would seem that such operations could easily be turned into a simple message passed to the file's source system for direct copying. Such a call could perhapes even be an async. operation with a method for querying progress via select/poll/kqueue.

- Jason

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