/*
* computes the average lifetime of all the blocks in a plane.
*/
double ssd_compute_avg_lifetime_in_plane(int plane_num, int elem_num, ssd_t *s)
{
int i;
int bitpos;
double tot_lifetime = 0;
ssd_element_metadata *metadata = &(s->elements[elem_num].metadata);
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);
tot_lifetime += metadata->block_usage[block].rem_lifetime;
}
return (tot_lifetime / s->params.blocks_per_plane);
}
void ssd_assert_valid_pages(int plane_num, ssd_element_metadata *metadata, ssd_t *s)
{
#if SSD_ASSERT_ALL
int i;
int block_valid_pages = 0;
int start_bitpos = plane_num * s->params.blocks_per_plane;
for (i = start_bitpos; i < (start_bitpos + (int)s->params.blocks_per_plane); i ++) {
int block = ssd_bitpos_to_block(i, s);
block_valid_pages += metadata->block_usage[block].num_valid;
}
ASSERT(block_valid_pages == metadata->plane_meta[plane_num].valid_pages);
#else
return;
#endif
}
int _ssd_alloc_log_block(int plane_num, int elem_num, ssd_t *s, int data_block){
ssd_element_metadata *metadata = &(s->elements[elem_num].metadata);
unsigned char *free_blocks = metadata->free_blocks;
int active_block = -1;
int prev_pos;
int bitpos;
int index;
if (plane_num != -1) {
prev_pos = metadata->plane_meta[plane_num].block_alloc_pos;
} else {
prev_pos = metadata->block_alloc_pos;
}
// find a free bit
bitpos = ssd_find_zero_bit(free_blocks, s->params.blocks_per_element, prev_pos);
ASSERT((bitpos >= 0) && (bitpos < s->params.blocks_per_element));
// check if we found the free bit in the plane we wanted to
if (plane_num != -1) {
if (ssd_bitpos_to_plane(bitpos, s) != plane_num) {
//printf("Error: We wanted a free block in plane %d but found another in %d\n",
// plane_num, ssd_bitpos_to_plane(bitpos, s));
//printf("So, starting the search again for plane %d\n", plane_num);
// start from the beginning
metadata->plane_meta[plane_num].block_alloc_pos = plane_num * s->params.blocks_per_plane;
prev_pos = metadata->plane_meta[plane_num].block_alloc_pos;
bitpos = ssd_find_zero_bit(free_blocks, s->params.blocks_per_element, prev_pos);
ASSERT((bitpos >= 0) && (bitpos < s->params.blocks_per_element));
if (ssd_bitpos_to_plane(bitpos, s) != plane_num) {
plane_num = ssd_bitpos_to_plane(bitpos, s);
}
}
metadata->plane_meta[plane_num].block_alloc_pos = \
(plane_num * s->params.blocks_per_plane) + ((bitpos+1) % s->params.blocks_per_plane);
} else {
metadata->block_alloc_pos = (bitpos+1) % s->params.blocks_per_element;
}
// find the block num
active_block = ssd_bitpos_to_block(bitpos, s);
if (active_block != -1) {
plane_metadata *pm;
// make sure we're doing the right thing
ASSERT(metadata->block_usage[active_block].plane_num == ssd_bitpos_to_plane(bitpos, s));
ASSERT(metadata->block_usage[active_block].bsn == 0);
ASSERT(metadata->block_usage[active_block].num_valid == 0);
ASSERT(metadata->block_usage[active_block].state == SSD_BLOCK_CLEAN);
if (plane_num == -1) {
plane_num = metadata->block_usage[active_block].plane_num;
} else {
ASSERT(plane_num == metadata->block_usage[active_block].plane_num);
}
pm = &metadata->plane_meta[plane_num];
// reduce the total number of free blocks
metadata->tot_free_blocks --;
pm->free_blocks --;
//assertion
ssd_assert_free_blocks(s, metadata);
// allocate the block
ssd_set_bit(free_blocks, bitpos);
metadata->block_usage[active_block].state = SSD_BLOCK_INUSE;
metadata->block_usage[active_block].bsn = metadata->bsn ++;
//ssd_assert_plane_freebits(plane_num, elem_num, metadata, s);
} else {
fprintf(outputfile3, "Error: cannot find a free block in ssd element %d\n", elem_num);
exit(-1);
}
metadata->num_log++;
index = ssd_index_search(s, metadata);
metadata->log_data[index].bsn = active_block;
metadata->log_data[index].data_block = data_block;
return index;
}
/*
* 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;
}