stasis-aries-wal/src/lladd/bufferPool.c

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/**
 * @file Implementation of in memory buffer pool
 *
 * $Id$
 * 
 */

/* _XOPEN_SOURCE is needed for posix_memalign */
#define _XOPEN_SOURCE 600
#include <stdlib.h>

#include <lladd/bufferPool.h>
#include <assert.h>
/* TODO:  Combine with buffer size... */
static int nextPage = 0;
static pthread_mutex_t pageMallocMutex;

static void * addressFromMalloc = 0;

/** We need one dummy page for locking purposes, so this array has one extra page in it. */
Page pool[MAX_BUFFER_SIZE+1];


void bufferPoolInit() { 

  nextPage = 0;
	
  pthread_mutex_init(&pageMallocMutex, NULL);

  byte * bufferSpace ;

#ifdef HAVE_POSIX_MEMALIGN
  int ret = posix_memalign((void*)&bufferSpace, PAGE_SIZE, PAGE_SIZE * (MAX_BUFFER_SIZE + 1));
  assert(!ret);
  addressFromMalloc = bufferSpace;
#else
  bufferSpace = malloc(PAGE_SIZE * (MAX_BUFFER_SIZE + 2));
  assert(bufferSpace);
  addressFromMalloc = bufferSpace;
  bufferSpace += PAGE_SIZE - (bufferSpace % PAGE_SIZE);
#endif

  for(int i = 0; i < MAX_BUFFER_SIZE+1; i++) {
    pool[i].rwlatch = initlock();
    pool[i].loadlatch = initlock();
    pool[i].memAddr = &(bufferSpace[i*PAGE_SIZE]);
  }
}

void bufferPoolDeInit() { 
  for(int i = 0; i < MAX_BUFFER_SIZE+1; i++) {
    deletelock(pool[i].rwlatch);
    deletelock(pool[i].loadlatch);
  }
  free(addressFromMalloc); // breaks efence
  pthread_mutex_destroy(&pageMallocMutex);
}

Page* pageMalloc() { 
  Page *page;

  pthread_mutex_lock(&pageMallocMutex);
  
  page = &(pool[nextPage]);
  
  nextPage++;
  /* There's a dummy page that we need to keep around, thus the +1 */
  assert(nextPage <= MAX_BUFFER_SIZE + 1); 

  pthread_mutex_unlock(&pageMallocMutex);

  return page;

}


static void pageFreeNoLock(Page *p, int id) {
  p->id = id;
  p->LSN = 0;
  p->dirty = 0;
}

/** @todo Does pageFree really need to obtain a lock? */
void pageFree(Page *p, int id) {
  writelock(p->rwlatch, 10);
  pageFreeNoLock(p,id);
  writeunlock(p->rwlatch);
}