The trouble with stable pages
The trouble with stable pages
Posted Mar 15, 2012 13:54 UTC (Thu) by slashdot (guest, #22014)In reply to: The trouble with stable pages by Spudd86
Parent article: The trouble with stable pages
I am suggesting to only do the copy if the application tries to access the page under writeback and takes the fault, which is hopefully relative rare (especially if the checksum is also delayed as you suggest).
With a single program, the worst that can happen is that the COW operation itself blocks because no pages are available, which is no worse than blocking on disk access.
Also, the additional pages are bound by the number of pages under writeback, which should be bounded by a value proportional to the number of simultaneous requests the hardware supports, which is small, so it shouldn't be an issue even with multiple programs.
And of course, systems with huge RAID arrays supporting bazillions of simultaneous request are also likely to have huge amounts of RAM.