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Synchronizing the Backing Store
IRIX writes modified pages to the backing store as infrequently as possible, in order to save time. When pages are locked, they are never written to backing store. This does not matter when the pages are ordinary data.
When the pages represent a file mapped into memory, you may want to force IRIX to write any modifications into the file. This creates a checkpoint, a known-good file state from which the program could resume.
The msync() function (see the msync(2) reference page) asks IRIX to write a specified segment to backing store. The segment must be a whole multiple of pages. You can optionally request
- synchronous writes, so the call does not return until the disk I/O is complete--ensuring that the data has been written
- page invalidation, so that the memory pages are released and will have to be reloaded from backing store if they are referenced again
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