Right, I think the point of boyer-moore is that it allows to eliminate / skip large chunks of the text during the search. So the assumption is that those pages

Right, I think the point of boyer-moore is that it allows to eliminate / skip large chunks of the text during the search. So the assumption is that those pages don't even ever get swapped in, but I think that'd only be the case when the pattern size is at least as large as the page size (usually 4KB!), which is not the case in the example in the mailing list. So the mystery continues!