On Thu, 15 Mar 2007 14:35:17 EDT, Rik van Riel said: > [EMAIL PROTECTED] wrote: > > On Wed, 14 Mar 2007 22:33:17 BST, Andreas Mohr said: > > > >> it'd seem we need some kind of state management here to figure out good > >> intervals of when to call mark_page_accessed() *again* for this page. E.g. > >> despite non-changing access patterns you could still call > >> mark_page_accessed() > >> every 32 calls or so to avoid expiry, but this would need extra helper > >> variables. > > > > What if you did something like > > > > if (jiffies%32) {... > > > > (Possibly scaling it so the low-order bits change). No need to lock it, as > > "right most of the time" is close enough. > > Bad idea. That way you would only count page accesses if the > phase of the moon^Wjiffie is just right.
On the other hand, Andreas suggested only marking it once every 32 calls, but that required a helper variable. Statistically, jiffies%32 should end up about the same as a helper variable %32. This of course, if just calling mark_page_accessed() is actually expensive enough that we don't want to do it unconditionally.
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