54 lines
2.2 KiB
C
54 lines
2.2 KiB
C
/**
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@file
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Implements cache replacement policies. Eventually, this could be
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extended to support application specific caching schemes.
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@todo Stasis used to use LRU-2S. LRU-2S is described in Markatos
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"On Caching Searching Engine Results". (This needs to be
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re-implemented properly.)
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For now, Stasis uses plain-old LRU. DB-MIN would be an interesting
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extension.
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*/
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#include <stasis/common.h>
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BEGIN_C_DECLS
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typedef struct replacementPolicy {
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/** Factory method */
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struct replacementPolicy* (*init)();
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/** Destructor */
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void (*deinit) (struct replacementPolicy* impl);
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/** The page has been touched. Reflect this fact (currently not called) */
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void (*hit) (struct replacementPolicy* impl, Page* page);
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/** Find a page that is "stale". Do not remove it.
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*
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* @deprecated This function is essentially impossible to use correctly in a concurrent setting, and is not necessarily threadsafe.
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* */
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Page* (*getStale)(struct replacementPolicy* impl);
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/** Remove a page from consideration. This method needs to increment the
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* "pinCount" field of Page (or perform other bookkeeping), since the page
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* may be removed multiple times before it is re-inserted. Pages that
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* have been removed should not be returned as "stale". */
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Page* (*remove) (struct replacementPolicy* impl, Page* page);
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/** Atomically getStale(), and remove() the page it returns.
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*
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* @return the page that was stale, and that has now been removed.
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*/
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Page* (*getStaleAndRemove)(struct replacementPolicy* impl);
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/** Insert a page into the replacement policy, and decrement the pinCount.
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* The page has just been "hit", and is now a candidate for getStale() to
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* consider (unless it has a non-zero pincount).
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*/
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void (*insert) (struct replacementPolicy* impl, Page* page);
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void * impl;
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} replacementPolicy;
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replacementPolicy * stasis_replacement_policy_lru_init();
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replacementPolicy * lruFastInit();
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replacementPolicy* replacementPolicyThreadsafeWrapperInit(replacementPolicy* rp);
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replacementPolicy* replacementPolicyConcurrentWrapperInit(replacementPolicy** rp, int count);
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replacementPolicy* replacementPolicyClockInit(Page * pageArray, int page_count);
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END_C_DECLS
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