/*
* makes sure that the number of free blocks is equal to the number
* of free bits in the bitmap block.
*/
void ssd_assert_plane_freebits(int plane_num, int elem_num, ssd_element_metadata *metadata, ssd_t *s)
{
int f1;
f1 = ssd_free_bits(plane_num, elem_num, metadata, s);
ASSERT(f1 == metadata->plane_meta[plane_num].free_blocks);
}
/*
* migrate data from a cold block to "to_blk"
*/
int ssd_migrate_cold_data(int to_blk, double *mcost, int plane_num, int elem_num, ssd_t *s)
{
int i;
int from_blk = -1;
double oldest_erase_time = simtime;
double cost = 0;
int bitpos;
#if SSD_ASSERT_ALL
int f1;
int f2;
#endif
ssd_element_metadata *metadata = &(s->elements[elem_num].metadata);
// first select the coldest of all blocks.
// one way to select is to find the one that has the oldest
// erasure time.
if (plane_num == -1) {
for (i = 0; i < s->params.blocks_per_element; i ++) {
if (metadata->block_usage[i].num_valid > 0) {
if (metadata->block_usage[i].time_of_last_erasure < oldest_erase_time) {
oldest_erase_time = metadata->block_usage[i].time_of_last_erasure;
from_blk = i;
}
}
}
} else {
#if SSD_ASSERT_ALL
f1 = ssd_free_bits(plane_num, elem_num, metadata, s);
ASSERT(f1 == metadata->plane_meta[metadata->block_usage[to_blk].plane_num].free_blocks);
#endif
bitpos = plane_num * s->params.blocks_per_plane;
for (i = bitpos; i < bitpos + (int)s->params.blocks_per_plane; i ++) {
int block = ssd_bitpos_to_block(i, s);
ASSERT(metadata->block_usage[block].plane_num == plane_num);
if (metadata->block_usage[block].num_valid > 0) {
if (metadata->block_usage[block].time_of_last_erasure < oldest_erase_time) {
oldest_erase_time = metadata->block_usage[block].time_of_last_erasure;
from_blk = block;
}
}
}
}
ASSERT(from_blk != -1);
if (plane_num != -1) {
ASSERT(metadata->block_usage[from_blk].plane_num == metadata->block_usage[to_blk].plane_num);
}
// next, clean the block to which we'll transfer the
// cold data
cost += _ssd_clean_block_fully(to_blk, metadata->block_usage[to_blk].plane_num, elem_num, metadata, s);
#if SSD_ASSERT_ALL
if (plane_num != -1) {
f2 = ssd_free_bits(plane_num, elem_num, metadata, s);
ASSERT(f2 == metadata->plane_meta[metadata->block_usage[to_blk].plane_num].free_blocks);
}
#endif
// then, migrate the cold data to the worn out block.
// for which, we first read all the valid data
cost += metadata->block_usage[from_blk].num_valid * s->params.page_read_latency;
// include the write cost
cost += metadata->block_usage[from_blk].num_valid * s->params.page_write_latency;
// if the src and dest blocks are on different planes
// include the transfer cost also
cost += ssd_crossover_cost(s, metadata, from_blk, to_blk);
// the cost of erasing the cold block (represented by from_blk)
// will be added later ...
// finally, update the metadata
metadata->block_usage[to_blk].bsn = metadata->block_usage[from_blk].bsn;
metadata->block_usage[to_blk].num_valid = metadata->block_usage[from_blk].num_valid;
metadata->block_usage[from_blk].num_valid = 0;
for (i = 0; i < s->params.pages_per_block; i ++) {
int lpn = metadata->block_usage[from_blk].page[i];
if (lpn != -1) {
ASSERT(metadata->lba_table[lpn] == (from_blk * s->params.pages_per_block + i));
metadata->lba_table[lpn] = to_blk * s->params.pages_per_block + i;
}
metadata->block_usage[to_blk].page[i] = metadata->block_usage[from_blk].page[i];
}
metadata->block_usage[to_blk].state = metadata->block_usage[from_blk].state;
bitpos = ssd_block_to_bitpos(s, to_blk);
ssd_set_bit(metadata->free_blocks, bitpos);
metadata->tot_free_blocks --;
metadata->plane_meta[metadata->block_usage[to_blk].plane_num].free_blocks --;
#if SSD_ASSERT_ALL
if (plane_num != -1) {
f2 = ssd_free_bits(plane_num, elem_num, metadata, s);
ASSERT(f2 == metadata->plane_meta[metadata->block_usage[to_blk].plane_num].free_blocks);
}
#endif
ssd_assert_free_blocks(s, metadata);
ASSERT(metadata->block_usage[from_blk].num_valid == 0);
#if ASSERT_FREEBITS
if (plane_num != -1) {
f2 = ssd_free_bits(plane_num, elem_num, metadata, s);
ASSERT(f1 == f2);
}
#endif
*mcost = cost;
// stat
metadata->tot_migrations ++;
metadata->tot_pgs_migrated += metadata->block_usage[to_blk].num_valid;
metadata->mig_cost += cost;
return from_blk;
}
