> > Is that generally the case on your systems? Every linux system I've
A simple log optimises writeout (which is latency critical) and can
otherwise stall an enitre system. In a log you can also have multiple
copies of the same page on disk easily, some stale - so you can write out
chunks of data that are not all them removed from memory, just so you get
them back more easily if you then do (and I guess you'd mark them
accordingly)
The second element is a cleaner - something to go around removing stuff
from the log that is needed when the disks are idle - and also to repack
data in nice linear chunks. So instead of using the empty disk time for
page-in you use it for packing data and optimising future paging.
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