static enum reassign_result_type do_slabs_reassign(int src, int dst) {
if (slab_rebalance_signal != 0)
return REASSIGN_RUNNING;
if (src == dst)
return REASSIGN_SRC_DST_SAME;
/* Special indicator to choose ourselves. */
if (src == -1) {
src = slabs_reassign_pick_any(dst);
/* TODO: If we end up back at -1, return a new error type */
}
if (src < POWER_SMALLEST || src > power_largest ||
dst < POWER_SMALLEST || dst > power_largest)
return REASSIGN_BADCLASS;
if (slabclass[src].slabs < 2)
return REASSIGN_NOSPARE;
slab_rebal.s_clsid = src;
slab_rebal.d_clsid = dst;
slab_rebalance_signal = 1;
pthread_cond_signal(&slab_rebalance_cond);
return REASSIGN_OK;
}
static enum reassign_result_type do_slabs_reassign(int src, int dst) {
if (slab_rebalance_signal != 0)
return REASSIGN_RUNNING;
if (src == dst)//不能相同
return REASSIGN_SRC_DST_SAME;
/* Special indicator to choose ourselves. */
if (src == -1) {//客户端命令要求随机选出一个源slab class
//选出一个页数大于1的slab class，并且该slab class不能是dst
//指定的那个。如果不存在这样的slab class，那么返回-1
src = slabs_reassign_pick_any(dst);
/* TODO: If we end up back at -1, return a new error type */
}
if (src < POWER_SMALLEST || src > power_largest ||
dst < POWER_SMALLEST || dst > power_largest)
return REASSIGN_BADCLASS;
//源slab class没有或者只有一个内存页，那么就不能分给别的slab class
if (slabclass[src].slabs < 2)
return REASSIGN_NOSPARE;
//全局变量slab_rebal
slab_rebal.s_clsid = src;//保存源slab class
slab_rebal.d_clsid = dst;//保存目标slab class
slab_rebalance_signal = 1;
//唤醒slab_rebalance_thread函数的线程
//在slabs_reassign函数中已经锁上了slabs_rebalance_lock
pthread_cond_signal(&slab_rebalance_cond);
return REASSIGN_OK;
}
