Everything I said is true for at least for Linux, where files are memory-mapped into the process space, and swapped page counts relate to anonymous pages (look at /proc/vmstat for the gory details; note that pgpgin/out and pswpin/out increment under different conditions).
OS X may admittedly be different. It's unfortunate that it doesn't expose more counters to help show what's really going on.
As for "reported pageouts are dirty memory pages being tossed" - where are they being tossed to, if not the filesystem?
They are usually being tossed to the pagefile (except in the case of read-write non-anonymous file mappings, which are not super common on OS X and which are functionally equivalent to paging to the page file anyway).
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Everything I said is true for at least for Linux, where files are memory-mapped into the process space, and swapped page counts relate to anonymous pages (look at /proc/vmstat for the gory details; note that pgpgin/out and pswpin/out increment under different conditions).
OS X may admittedly be different. It's unfortunate that it doesn't expose more counters to help show what's really going on.
As for "reported pageouts are dirty memory pages being tossed" - where are they being tossed to, if not the filesystem?
They are usually being tossed to the pagefile (except in the case of read-write non-anonymous file mappings, which are not super common on OS X and which are functionally equivalent to paging to the page file anyway).
On OS X files aren't memory-mapped by default.