static int ssd_pick_block_to_clean(int plane_num, int elem_num, ssd_element_metadata *metadata, ssd_t *s)
{
int block;
int log_block;
int lbn;
int min_valid = s->params.pages_per_block * 2;
int i,j;
double avg_lifetime = 1;
unsigned int reserved_blocks_per_plane = (s->params.reserve_blocks * s->params.blocks_per_plane) / 100;
unsigned int usable_blocks_per_plane = s->params.blocks_per_plane - reserved_blocks_per_plane;
unsigned int reserved_blocks = reserved_blocks_per_plane * s->params.planes_per_pkg;
unsigned int usable_blocks = usable_blocks_per_plane * s->params.planes_per_pkg;
int num_valid;
avg_lifetime = ssd_compute_avg_lifetime(plane_num, elem_num, s);
for(i = 0; i < usable_blocks ; i++) {
block = metadata->lba_table[i];
if(block == -1){
continue;
}
if( metadata->block_usage[block].log_index == -1){
continue;
}
log_block = metadata->log_data[metadata->block_usage[block].log_index].bsn;
num_valid = metadata->block_usage[block].num_valid + metadata->block_usage[log_block].num_valid;
if(num_valid < min_valid) {
/*min_valid = metadata->block_usage[block].num_valid;
if(_ssd_pick_block_to_clean(block, plane_num, elem_num, metadata, s)){
int mig_blk;
block_metadata bm;
bm = metadata->block_usage[block];
mig_blk = ssd_pick_wear_aware_with_migration(bm.block_num, bm.rem_lifetime, avg_lifetime, mcost, bm.plane_num, elem_num, s);
if (ssd_pick_wear_aware(bm.block_num, bm.rem_lifetime, avg_lifetime, s)) {
lbn = i;
break;
}
}*/
lbn = i;
}
}
return lbn;
}
/*
* first we create a hash table of blocks according to their
* usage. then we select blocks with the least usage and clean
* them.
*/
static double ssd_clean_blocks_greedy(int plane_num, int elem_num, ssd_t *s)
{
double cost = 0;
double avg_lifetime;
int i;
usage_table *table;
ssd_element_metadata *metadata = &(s->elements[elem_num].metadata);
/////////////////////////////////////////////////////////////////////////////
// build the histogram
table = ssd_build_usage_table(elem_num, s);
//////////////////////////////////////////////////////////////////////////////
// find the average life time of all the blocks in this element
avg_lifetime = ssd_compute_avg_lifetime(plane_num, elem_num, s);
/////////////////////////////////////////////////////////////////////////////
// we now have a hash table of blocks, where the key of each
// bucket is the usage count and each bucket has all the blocks with
// the same usage count (i.e., the same num of valid pages).
for (i = 0; i <= s->params.pages_per_block; i ++) {
int j;
usage_table *entry;
// get the bucket of blocks with 'i' valid pages
entry = &(table[i]);
// free all the blocks with 'i' valid pages
for (j = 0; j < entry->len; j ++) {
int blk = entry->block[j];
int block_life = metadata->block_usage[blk].rem_lifetime;
// if this is plane specific cleaning, then skip all the
// blocks that don't belong to this plane.
if ((plane_num != -1) && (metadata->block_usage[blk].plane_num != plane_num)) {
continue;
}
// if the block is already dead, skip it
if (block_life == 0) {
continue;
}
// clean only those blocks that are sealed.
if (ssd_can_clean_block(s, metadata, blk)) {
// if we care about wear-leveling, then we must rate limit overly cleaned blocks
if (s->params.cleaning_policy == DISKSIM_SSD_CLEANING_POLICY_GREEDY_WEAR_AWARE) {
// see if this block's remaining lifetime is within
// a certain threshold of the average remaining lifetime
// of all blocks in this element
if (block_life < (SSD_LIFETIME_THRESHOLD_X * avg_lifetime)) {
// we have to rate limit this block as it has exceeded
// its cleaning limits
printf("Rate limiting block %d (block life %d avg life %f\n",
blk, block_life, avg_lifetime);
if (ssd_rate_limit(block_life, avg_lifetime)) {
// skip this block and go to the next one
continue;
}
}
}
// okies, finally here we're with the block to be cleaned.
// invoke cleaning until we reach the high watermark.
cost += _ssd_clean_block_fully(blk, metadata->block_usage[blk].plane_num, elem_num, metadata, s);
if (ssd_stop_cleaning(plane_num, elem_num, s)) {
// no more cleaning is required -- so quit.
break;
}
}
}
if (ssd_stop_cleaning(plane_num, elem_num, s)) {
// no more cleaning is required -- so quit.
break;
}
}
// release the table
ssd_release_usage_table(table, s);
// see if we were able to generate enough free blocks
if (!ssd_stop_cleaning(plane_num, elem_num, s)) {
printf("Yuck! we couldn't generate enough free pages in plane %d elem %d ssd %d\n",
plane_num, elem_num, s->devno);
}
return cost;
}
/*
* a greedy solution, where we find the block in a plane with the least
* num of valid pages and return it.
*/
static int ssd_pick_block_to_clean2(int plane_num, int elem_num, double *mcost, ssd_element_metadata *metadata, ssd_t *s)
{
double avg_lifetime = 1;
int i;
int size;
int block = -1;
int min_valid = s->params.pages_per_block - 1; // one page goes for the summary info
listnode *greedy_list;
*mcost = 0;
// find the average life time of all the blocks in this element
avg_lifetime = ssd_compute_avg_lifetime(plane_num, elem_num, s);
// we create a list of greedily selected blocks
ll_create(&greedy_list);
for (i = 0; i < s->params.blocks_per_element; i ++) {
if (_ssd_pick_block_to_clean(i, plane_num, elem_num, metadata, s)) {
// greedily select the block
if (metadata->block_usage[i].num_valid <= min_valid) {
ASSERT(i == metadata->block_usage[i].block_num);
ll_insert_at_head(greedy_list, (void*)&metadata->block_usage[i]);
min_valid = metadata->block_usage[i].num_valid;
block = i;
}
}
}
ASSERT(block != -1);
block = -1;
// from the greedily picked blocks, select one after rate
// limiting the overly used blocks
size = ll_get_size(greedy_list);
//printf("plane %d elem %d size %d avg lifetime %f\n",
// plane_num, elem_num, size, avg_lifetime);
for (i = 0; i < size; i ++) {
block_metadata *bm;
int mig_blk;
listnode *n = ll_get_nth_node(greedy_list, i);
bm = ((block_metadata *)n->data);
if (i == 0) {
ASSERT(min_valid == bm->num_valid);
}
// this is the last of the greedily picked blocks.
if (i == size -1) {
// select it!
block = bm->block_num;
break;
}
if (s->params.cleaning_policy == DISKSIM_SSD_CLEANING_POLICY_GREEDY_WEAR_AGNOSTIC) {
block = bm->block_num;
break;
} else {
#if MIGRATE
// migration
mig_blk = ssd_pick_wear_aware_with_migration(bm->block_num, bm->rem_lifetime, avg_lifetime, mcost, bm->plane_num, elem_num, s);
if (mig_blk != bm->block_num) {
// data has been migrated and we have a new
// block to use
block = mig_blk;
break;
}
#endif
// pick this block giving consideration to its life time
if (ssd_pick_wear_aware(bm->block_num, bm->rem_lifetime, avg_lifetime, s)) {
block = bm->block_num;
break;
}
}
}
ll_release(greedy_list);
ASSERT(block != -1);
return block;
}
//prints the cleaning algo statistics
void ssd_printcleanstats(int *set, int setsize, char *sourcestr)
{
int i;
int tot_ssd = 0;
int elts_count = 0;
double iops = 0;
fprintf(outputfile, "\n\nSSD CLEANING STATISTICS\n");
fprintf(outputfile, "---------------------------------------------\n\n");
for (i = 0; i < setsize; i ++) {
int j;
int tot_elts = 0;
ssd_t *s = getssd(set[i]);
if (s->params.write_policy == DISKSIM_SSD_WRITE_POLICY_OSR) {
elts_count += s->params.nelements;
for (j = 0; j < s->params.nelements; j ++) {
int plane_num;
double avg_lifetime;
double elem_iops = 0;
double elem_clean_iops = 0;
ssd_element_stat *stat = &(s->elements[j].stat);
avg_lifetime = ssd_compute_avg_lifetime(-1, j, s);
fprintf(outputfile, "%s #%d elem #%d Total reqs issued:\t%d\n",
sourcestr, set[i], j, s->elements[j].stat.tot_reqs_issued);
fprintf(outputfile, "%s #%d elem #%d Total time taken:\t%f\n",
sourcestr, set[i], j, s->elements[j].stat.tot_time_taken);
if (s->elements[j].stat.tot_time_taken > 0) {
elem_iops = ((s->elements[j].stat.tot_reqs_issued*1000.0)/s->elements[j].stat.tot_time_taken);
fprintf(outputfile, "%s #%d elem #%d IOPS:\t%f\n",
sourcestr, set[i], j, elem_iops);
}
fprintf(outputfile, "%s #%d elem #%d Total cleaning reqs issued:\t%d\n",
sourcestr, set[i], j, s->elements[j].stat.num_clean);
fprintf(outputfile, "%s #%d elem #%d Total cleaning time taken:\t%f\n",
sourcestr, set[i], j, s->elements[j].stat.tot_clean_time);
fprintf(outputfile, "%s #%d elem #%d Total migrations:\t%d\n",
sourcestr, set[i], j, s->elements[j].metadata.tot_migrations);
fprintf(outputfile, "%s #%d elem #%d Total pages migrated:\t%d\n",
sourcestr, set[i], j, s->elements[j].metadata.tot_pgs_migrated);
fprintf(outputfile, "%s #%d elem #%d Total migrations cost:\t%f\n",
sourcestr, set[i], j, s->elements[j].metadata.mig_cost);
if (s->elements[j].stat.tot_clean_time > 0) {
elem_clean_iops = ((s->elements[j].stat.num_clean*1000.0)/s->elements[j].stat.tot_clean_time);
fprintf(outputfile, "%s #%d elem #%d clean IOPS:\t%f\n",
sourcestr, set[i], j, elem_clean_iops);
}
fprintf(outputfile, "%s #%d elem #%d Overall IOPS:\t%f\n",
sourcestr, set[i], j, ((s->elements[j].stat.num_clean+s->elements[j].stat.tot_reqs_issued)*1000.0)/(s->elements[j].stat.tot_clean_time+s->elements[j].stat.tot_time_taken));
iops += elem_iops;
fprintf(outputfile, "%s #%d elem #%d Number of free blocks:\t%d\n",
sourcestr, set[i], j, s->elements[j].metadata.tot_free_blocks);
fprintf(outputfile, "%s #%d elem #%d Number of cleans:\t%d\n",
sourcestr, set[i], j, stat->num_clean);
fprintf(outputfile, "%s #%d elem #%d Pages moved:\t%d\n",
sourcestr, set[i], j, stat->pages_moved);
fprintf(outputfile, "%s #%d elem #%d Total xfer time:\t%f\n",
sourcestr, set[i], j, stat->tot_xfer_cost);
if (stat->tot_xfer_cost > 0) {
fprintf(outputfile, "%s #%d elem #%d Xfer time per page:\t%f\n",
sourcestr, set[i], j, stat->tot_xfer_cost/(1.0*stat->pages_moved));
} else {
fprintf(outputfile, "%s #%d elem #%d Xfer time per page:\t0\n",
sourcestr, set[i], j);
}
fprintf(outputfile, "%s #%d elem #%d Average lifetime:\t%f\n",
sourcestr, set[i], j, avg_lifetime);
fprintf(outputfile, "%s #%d elem #%d Plane Level Statistics\n",
sourcestr, set[i], j);
fprintf(outputfile, "%s #%d elem #%d ", sourcestr, set[i], j);
for (plane_num = 0; plane_num < s->params.planes_per_pkg; plane_num ++) {
fprintf(outputfile, "%d:(%d) ",
plane_num, s->elements[j].metadata.plane_meta[plane_num].num_cleans);
}
fprintf(outputfile, "\n");
ssd_print_block_lifetime_distribution(j, s, set[i], avg_lifetime, sourcestr);
fprintf(outputfile, "\n");
tot_elts += stat->pages_moved;
}
//fprintf(outputfile, "%s SSD %d average # of pages moved per element %d\n",
// sourcestr, set[i], tot_elts / s->params.nelements);
tot_ssd += tot_elts;
fprintf(outputfile, "\n");
}
}
if (elts_count > 0) {
fprintf(outputfile, "%s Total SSD IOPS:\t%f\n",
sourcestr, iops);
fprintf(outputfile, "%s Average SSD element IOPS:\t%f\n",
sourcestr, iops/elts_count);
}
//fprintf(outputfile, "%s SSD average # of pages moved per ssd %d\n\n",
// sourcestr, tot_ssd / setsize);
}
