I feared that.Moving the Cache Directory Block (cdb) on a hit to the MRU position of the appropriate queue "is the bookkeeping" of this strategy. The whole algorithm is based on it, and I don't see yet how to avoid that without opening a huge can of worms that look like deadlocks. But I'll think about it for a while.
Are there strategies that do not rely on a global lock? The Linux kernel uses a lazy LRU with referenced bits: on access, the referenced bit is set. The freespace logic takes pages from the end of a linked list, and checks that bit: if it's set, then the page is moved back to the top of the list. Otherwise it's a candidate for replacement. Pages start at the head of that pseudo-lru list, with the reference bit clear: that way a page that is accessed only once has a lower priority than a frequently accessed page. At least that's how I understand the algorithm.
-- Manfred
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