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#ifndef lint
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static const char RCSid[] = "$Id$";
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#endif
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/*
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=======================================================================
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Cache for out-of-core octree.
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Uses an LRU page replacement scheme. Page table nodes are stored in
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order of reference in a doubly linked list, with the most recently used
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(MRU) page at the head, and the least recently used (LRU) at the tail.
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Nodes are referenced by the page's base address via a hashtable for
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constant time access (in the absence of hash collisions). Hash
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collisions can be limited by adjusting the hashtable load factor
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OOC_CACHE_LOAD; this is the fraction of the number of pages that will
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actually be cached.
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Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
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(c) Lucerne University of Applied Sciences and Arts,
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supported by the Swiss National Science Foundation (SNSF, #147053)
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=======================================================================
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$Id: ooccache.c,v 2.1 2016/05/17 17:39:47 rschregle Exp $
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*/
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#if !defined(_WIN32) && !defined(_WIN64) || defined(PMAP_OOC)
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/* No Windoze support for now */
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#include <stdlib.h>
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#include <unistd.h>
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#include "ooccache.h"
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static OOC_CacheIdx OOC_PrevPrime (OOC_CacheIdx n)
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/* Return largest prime number <= n */
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{
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OOC_CacheIdx n2 = n + 1, i;
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do {
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n2--;
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for (i = 2; n2 % i && i <= n2 >> 1; i++);
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} while (!(n2 % i));
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return n2;
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}
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int OOC_CacheInit (OOC_Cache *cache, unsigned numPages,
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unsigned recPerPage, unsigned recSize)
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{
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OOC_CacheIdx i;
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if (!cache)
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return -1;
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/* Clamp number of pages if necessary */
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if (numPages < OOC_CACHE_MINPAGES) {
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numPages = OOC_CACHE_MINPAGES;
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fputs("OOC_CacheInit: clamping num pages to min\n", stderr);
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}
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if (numPages >= OOC_CACHEIDX_NULL) {
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numPages = OOC_CACHEIDX_NULL - 1;
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fputs("OOC_CacheInit: clamping num pages to max\n", stderr);
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}
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/* Round numPages to next prime to reduce hash clustering & collisions */
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numPages = OOC_PrevPrime(numPages);
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cache -> recPerPage = recPerPage;
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cache -> numPages = numPages;
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cache -> recSize = recSize;
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cache -> pageSize = (unsigned long)cache -> recPerPage *
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cache -> recSize;
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cache -> pageCnt = 0;
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cache -> numHits = cache -> numReads = cache -> numColl =
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cache -> numRept = 0;
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cache -> mru = cache -> lru = OOC_CACHEIDX_NULL;
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cache -> lastKey = 0;
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cache -> lastPage = NULL;
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/* Allocate & init hashtable */
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if (!(cache -> pageTable = calloc(numPages, sizeof(OOC_CacheNode)))) {
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perror("OOC_InitCache: failed pagetable allocation");
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return -1;
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}
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for (i = 0; i < numPages; i++) {
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cache -> pageTable [i].data = NULL;
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cache -> pageTable [i].key = 0;
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cache -> pageTable [i].prev = cache -> pageTable [i].next =
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OOC_CACHEIDX_NULL;
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}
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#ifdef OOC_CACHE_STATS
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fprintf(stderr,
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"OOC_InitCache: caching %d pages @ %d records (%.2f Mb)\n",
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cache -> numPages, cache -> recPerPage,
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(float)cache -> numPages * cache -> pageSize / (1L << 20));
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#endif
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return 0;
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}
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static OOC_CacheIdx OOC_CacheFind (OOC_Cache *cache, OOC_CacheKey key)
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/* Return index to pagetable node for given key; collisions are resolved
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* via the probe sequence defined by OOC_CACHE_NEXT() */
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{
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OOC_CacheIdx idx = OOC_CACHE_HASH(key, cache -> numPages);
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OOC_CacheNode *page = cache -> pageTable + idx;
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/* Find matching pagetable node starting from idx and stop at the first
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* empty node; a full table would result in an infinite loop! */
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while (page -> data && page -> key != key) {
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idx = OOC_CACHE_NEXT(idx, cache -> numPages);
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page = cache -> pageTable + idx;
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cache -> numColl++;
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}
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return idx;
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}
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static void OOC_CacheUnlink (OOC_Cache *cache, OOC_CacheIdx pageIdx)
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/* Unlink page from history chain, updating LRU in cache if necessary */
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{
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OOC_CacheNode *page = cache -> pageTable + pageIdx;
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/* Unlink prev/next index */
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if (page -> prev != OOC_CACHEIDX_NULL)
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cache -> pageTable [page -> prev].next = page -> next;
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if (page -> next != OOC_CACHEIDX_NULL)
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cache -> pageTable [page -> next].prev = page -> prev;
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/* Update LRU index */
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if (pageIdx == cache -> lru)
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cache -> lru = page -> prev;
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}
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static void OOC_CacheRelink (OOC_Cache *cache, OOC_CacheIdx pageIdx)
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/* Update history chain with new page index */
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{
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OOC_CacheNode *page = cache -> pageTable + pageIdx;
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if (page -> prev != OOC_CACHEIDX_NULL)
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cache -> pageTable [page -> prev].next = pageIdx;
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if (page -> next != OOC_CACHEIDX_NULL)
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cache -> pageTable [page -> next].prev = pageIdx;
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}
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static void OOC_CacheSetMRU (OOC_Cache *cache, OOC_CacheIdx pageIdx)
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/* Set page as most recently used and move to head of history chain */
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{
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OOC_CacheNode *page = cache -> pageTable + pageIdx;
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OOC_CacheUnlink(cache, pageIdx);
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page -> prev = OOC_CACHEIDX_NULL;
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page -> next = cache -> mru;
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cache -> pageTable [cache -> mru].prev = pageIdx;
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cache -> mru = pageIdx;
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}
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static void *OOC_CacheDelete (OOC_Cache *cache, OOC_CacheIdx pageIdx)
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/* Delete cache node at pageIdx and tidy up fragmentation in pagetable to
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* minimise collisions. Returns pointer to deleted node's page data
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*
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* !!! Note cache -> pageCnt is NOT decremented as this is immediately
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* !!! followed by a call to OOC_CacheNew() in OOC_CacheData() */
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{
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OOC_CacheNode *page = cache -> pageTable + pageIdx, *nextPage;
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OOC_CacheIdx nextIdx;
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void *delData = page -> data, *nextData;
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/* Unlink page from history chain */
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OOC_CacheUnlink(cache, pageIdx);
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/* Free pagetable node */
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page -> data = NULL;
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nextIdx = OOC_CACHE_NEXT(pageIdx, cache -> numPages);
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nextPage = cache -> pageTable + nextIdx;
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/* Close gaps in probe sequence until empty node found */
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while ((nextData = nextPage -> data)) {
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/* Mark next node as free and reprobe for its key */
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nextPage -> data = NULL;
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pageIdx = OOC_CacheFind(cache, nextPage -> key);
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page = cache -> pageTable + pageIdx;
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/* Set page data pointer & reactivate page */
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page -> data = nextData;
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if (pageIdx != nextIdx) {
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/* Next page maps to freed node; relocate to close gap and update
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* history chain and LRU/MRU if necessary */
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page -> key = nextPage -> key; /* memcpy() faster ? */
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page -> prev = nextPage -> prev;
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page -> next = nextPage -> next;
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OOC_CacheRelink(cache, pageIdx);
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if (cache -> lru == nextIdx)
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cache -> lru = pageIdx;
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if (cache -> mru == nextIdx)
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cache -> mru = pageIdx;
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}
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nextIdx = OOC_CACHE_NEXT(nextIdx, cache -> numPages);
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nextPage = cache -> pageTable + nextIdx;
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}
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return delData;
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}
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static OOC_CacheNode *OOC_CacheNew (OOC_Cache *cache, OOC_CacheIdx pageIdx,
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OOC_CacheKey pageKey, void *pageData)
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/* Init new pagetable node with given index, key and data. Returns pointer
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* to new node */
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{
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OOC_CacheNode *page = cache -> pageTable + pageIdx;
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page -> prev = page -> next = OOC_CACHEIDX_NULL;
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page -> key = pageKey;
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page -> data = pageData;
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return page;
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}
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#ifdef OOC_CACHE_CHECK
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static int OOC_CacheCheck (OOC_Cache *cache)
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/* Run sanity checks on hashtable and page list */
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{
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OOC_CacheIdx i, pageCnt = 0;
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OOC_CacheNode *page;
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/* Check pagetable mapping */
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for (i = 0, page = cache->pageTable; i < cache->numPages; i++, page++)
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if (page -> data) {
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/* Check hash func maps page key to this node */
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if (OOC_CacheFind(cache, page -> key) != i) {
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fputs("OOC_CacheCheck: hashing inconsistency\n", stderr);
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return -1;
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}
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pageCnt++;
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}
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if (pageCnt != cache -> pageCnt) {
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fputs("OOC_CacheCheck: pagetable count inconsistency\n", stderr);
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return -1;
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}
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if (cache -> mru == OOC_CACHEIDX_NULL ||
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cache -> lru == OOC_CACHEIDX_NULL) {
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fputs("OOC_CacheCheck: undefined MRU/LRU\n", stderr);
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return -1;
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}
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pageCnt = 0;
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i = cache -> mru;
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/* Check page history */
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while (i != OOC_CACHEIDX_NULL) {
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/* Check link to previous page (should be none for MRU) */
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page = cache -> pageTable + i;
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if (i == cache -> mru)
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if (page -> prev != OOC_CACHEIDX_NULL) {
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fputs("OOC_CacheCheck: MRU inconsistency\n", stderr);
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return -1;
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}
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else;
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else if (page -> prev == OOC_CACHEIDX_NULL ||
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cache -> pageTable [page -> prev].next != i) {
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fputs("OOC_CacheCheck: prev page inconsistency\n", stderr);
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return -1;
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}
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/* Check link to next page node (should be none for LRU) */
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if (i == cache -> lru)
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if (page -> next != OOC_CACHEIDX_NULL) {
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fputs("OOC_CacheCheck: LRU inconsistency\n", stderr);
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return -1;
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}
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else;
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else if (page -> next != OOC_CACHEIDX_NULL &&
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cache -> pageTable [page -> next].prev != i) {
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fputs("OOC_CacheCheck: next page inconsistency\n", stderr);
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return -1;
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}
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/* Check LRU is at tail of page history */
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if (page -> next == OOC_CACHEIDX_NULL && i != cache -> lru) {
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fputs("OOC_CacheCheck: page history tail not LRU\n", stderr);
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return -1;
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}
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i = page -> next;
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pageCnt++;
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}
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if (pageCnt != cache -> pageCnt) {
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fputs("OOC_CacheCheck: page history count inconsistency\n", stderr);
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return -1;
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}
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return 0;
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}
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#endif
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void *OOC_CacheData (OOC_Cache *cache, FILE *file, unsigned long recIdx)
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{
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const OOC_CacheKey pageKey = recIdx / cache -> recPerPage;
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OOC_CacheNode *page = NULL;
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/* We assume locality of reference, and that it's likely the same page
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* will therefore be accessed sequentially; in this case we just reuse
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* the pagetable index */
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if (pageKey != cache -> lastKey || !cache -> pageCnt) {
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OOC_CacheIdx pageIdx = OOC_CacheFind(cache, pageKey);
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void *pageData;
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page = cache -> pageTable + pageIdx;
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if (!page -> data) {
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/* Page not cached; insert in pagetable */
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const unsigned long filePos = cache -> pageSize * pageKey;
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if (cache -> pageCnt < OOC_CACHE_LOAD * cache -> numPages) {
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/* Cache not fully loaded; allocate new page data */
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if (!(pageData = calloc(cache -> recPerPage, cache -> recSize))) {
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perror("OOC_CacheData: failed page allocation");
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return NULL;
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}
|
| 357 |
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| 358 |
/* Init LRU and MRU if necessary */
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| 359 |
if (cache -> mru == OOC_CACHEIDX_NULL ||
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cache -> lru == OOC_CACHEIDX_NULL)
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cache -> mru = cache -> lru = pageIdx;
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cache -> pageCnt++;
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}
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else {
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/* Cache fully loaded; adding more entries would aggravate
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* hash collisions, so evict LRU page. We reuse its
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* allocated page data and then overwrite it. */
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pageData = OOC_CacheDelete(cache, cache -> lru);
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/* Update page index as it may have moved forward in probe
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* sequence after deletion */
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pageIdx = OOC_CacheFind(cache, pageKey);
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}
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| 376 |
/* Init new pagetable node, will be linked in history below */
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| 377 |
page = OOC_CacheNew(cache, pageIdx, pageKey, pageData);
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| 379 |
/* Load page data from file; the last page may be truncated */
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| 380 |
if (!pread(fileno(file), page -> data, cache -> pageSize, filePos)) {
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| 381 |
fputs("OOC_CacheData: failed seek/read from data stream", stderr);
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| 382 |
return NULL;
|
| 383 |
}
|
| 384 |
}
|
| 385 |
else
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| 386 |
/* Page in cache */
|
| 387 |
cache -> numHits++;
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| 388 |
|
| 389 |
if (cache -> mru != pageIdx)
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/* Cached page is now most recently used; unlink and move to front
|
| 391 |
* of history chain and update MRU */
|
| 392 |
OOC_CacheSetMRU(cache, pageIdx);
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| 393 |
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| 394 |
/* Update last page to detect repeat accesses */
|
| 395 |
cache -> lastKey = pageKey;
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| 396 |
cache -> lastPage = page;
|
| 397 |
}
|
| 398 |
else {
|
| 399 |
/* Repeated page, skip hashing and just reuse last page */
|
| 400 |
page = cache -> lastPage;
|
| 401 |
cache -> numHits++;
|
| 402 |
cache -> numRept++;
|
| 403 |
}
|
| 404 |
|
| 405 |
cache -> numReads++;
|
| 406 |
|
| 407 |
#ifdef OOC_CACHE_CHECK
|
| 408 |
if (OOC_CacheCheck(cache))
|
| 409 |
return NULL;
|
| 410 |
#endif
|
| 411 |
|
| 412 |
/* Return pointer to record within cached page */
|
| 413 |
return page -> data + (recIdx % cache -> recPerPage) * cache -> recSize;
|
| 414 |
}
|
| 415 |
|
| 416 |
|
| 417 |
|
| 418 |
void OOC_DeleteCache (OOC_Cache *cache)
|
| 419 |
{
|
| 420 |
OOC_CacheIdx i;
|
| 421 |
|
| 422 |
for (i = 0; i < cache -> numPages; i++)
|
| 423 |
if (cache -> pageTable [i].data)
|
| 424 |
free(cache -> pageTable [i].data);
|
| 425 |
|
| 426 |
free(cache -> pageTable);
|
| 427 |
cache -> pageTable = NULL;
|
| 428 |
cache -> pageCnt = 0;
|
| 429 |
cache -> mru = cache -> lru = OOC_CACHEIDX_NULL;
|
| 430 |
}
|
| 431 |
|
| 432 |
#endif /* NIX / PMAP_OOC */
|
