lightnvm: pblk: redesign GC algorithm

At the moment, in order to get enough read parallelism, we have recycled
several lines at the same time. This approach has proven not to work
well when reaching capacity, since we end up mixing valid data from all
lines, thus not maintaining a sustainable free/recycled line ratio.

The new design, relies on a two level workqueue mechanism. In the first
level, we read the metadata for a number of lines based on the GC list
they reside on (this is governed by the number of valid sectors in each
line). In the second level, we recycle a single line at a time. Here, we
issue reads in parallel, while a single GC write thread places data in
the write buffer. This design allows to (i) only move data from one line
at a time, thus maintaining a sane free/recycled ration and (ii)
maintain the GC writer busy with recycled data.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 43 deletions

diff --git a/drivers/lightnvm/pblk-sysfs.c b/drivers/lightnvm/pblk-sysfs.c
index e1e92c9498a9..d9f7f13a38cc 100644
--- a/drivers/lightnvm/pblk-sysfs.c
+++ b/drivers/lightnvm/pblk-sysfs.c
@@ -49,30 +49,26 @@ static ssize_t pblk_sysfs_luns_show(struct pblk *pblk, char *page)
 
 static ssize_t pblk_sysfs_rate_limiter(struct pblk *pblk, char *page)
 {
-	struct nvm_tgt_dev *dev = pblk->dev;
-	struct nvm_geo *geo = &dev->geo;
 	int free_blocks, total_blocks;
 	int rb_user_max, rb_user_cnt;
-	int rb_gc_max, rb_gc_rsv, rb_gc_cnt, rb_budget, rb_state;
+	int rb_gc_max, rb_gc_cnt, rb_budget, rb_state;
 
 	free_blocks = atomic_read(&pblk->rl.free_blocks);
 	rb_user_max = pblk->rl.rb_user_max;
 	rb_user_cnt = atomic_read(&pblk->rl.rb_user_cnt);
 	rb_gc_max = pblk->rl.rb_gc_max;
-	rb_gc_rsv = pblk->rl.rb_gc_rsv;
 	rb_gc_cnt = atomic_read(&pblk->rl.rb_gc_cnt);
 	rb_budget = pblk->rl.rb_budget;
 	rb_state = pblk->rl.rb_state;
 
-	total_blocks = geo->blks_per_lun * geo->nr_luns;
+	total_blocks = pblk->rl.total_blocks;
 
 	return snprintf(page, PAGE_SIZE,
-		"u:%u/%u,gc:%u/%u/%u(%u/%u)(stop:<%u,full:>%u,free:%d/%d)-%d\n",
+		"u:%u/%u,gc:%u/%u(%u/%u)(stop:<%u,full:>%u,free:%d/%d)-%d\n",
 				rb_user_cnt,
 				rb_user_max,
 				rb_gc_cnt,
 				rb_gc_max,
-				rb_gc_rsv,
 				rb_state,
 				rb_budget,
 				pblk->rl.low,
@@ -237,7 +233,8 @@ static ssize_t pblk_sysfs_lines(struct pblk *pblk, char *page)
 	spin_unlock(&l_mg->free_lock);
 
 	if (nr_free_lines != free_line_cnt)
-		pr_err("pblk: corrupted free line list\n");
+		pr_err("pblk: corrupted free line list:%d/%d\n",
+						nr_free_lines, free_line_cnt);
 
 	sz = snprintf(page, PAGE_SIZE - sz,
 		"line: nluns:%d, nblks:%d, nsecs:%d\n",
@@ -319,32 +316,11 @@ static ssize_t pblk_sysfs_stats_debug(struct pblk *pblk, char *page)
 }
 #endif
 
-static ssize_t pblk_sysfs_rate_store(struct pblk *pblk, const char *page,
-				     size_t len)
-{
-	struct pblk_gc *gc = &pblk->gc;
-	size_t c_len;
-	int value;
-
-	c_len = strcspn(page, "\n");
-	if (c_len >= len)
-		return -EINVAL;
-
-	if (kstrtouint(page, 0, &value))
-		return -EINVAL;
-
-	spin_lock(&gc->lock);
-	pblk_rl_set_gc_rsc(&pblk->rl, value);
-	spin_unlock(&gc->lock);
-
-	return len;
-}
-
 static ssize_t pblk_sysfs_gc_force(struct pblk *pblk, const char *page,
 				   size_t len)
 {
 	size_t c_len;
-	int force;
+	int ret, force;
 
 	c_len = strcspn(page, "\n");
 	if (c_len >= len)
@@ -353,10 +329,7 @@ static ssize_t pblk_sysfs_gc_force(struct pblk *pblk, const char *page,
 	if (kstrtouint(page, 0, &force))
 		return -EINVAL;
 
-	if (force < 0 || force > 1)
-		return -EINVAL;
-
-	pblk_gc_sysfs_force(pblk, force);
+	ret = pblk_gc_sysfs_force(pblk, force);
 
 	return len;
 }
@@ -434,11 +407,6 @@ static struct attribute sys_max_sec_per_write = {
 	.mode = 0644,
 };
 
-static struct attribute sys_gc_rl_max = {
-	.name = "gc_rl_max",
-	.mode = 0200,
-};
-
 #ifdef CONFIG_NVM_DEBUG
 static struct attribute sys_stats_debug_attr = {
 	.name = "stats",
@@ -453,7 +421,6 @@ static struct attribute *pblk_attrs[] = {
 	&sys_gc_state,
 	&sys_gc_force,
 	&sys_max_sec_per_write,
-	&sys_gc_rl_max,
 	&sys_rb_attr,
 	&sys_stats_ppaf_attr,
 	&sys_lines_attr,
@@ -499,9 +466,7 @@ static ssize_t pblk_sysfs_store(struct kobject *kobj, struct attribute *attr,
 {
 	struct pblk *pblk = container_of(kobj, struct pblk, kobj);
 
-	if (strcmp(attr->name, "gc_rl_max") == 0)
-		return pblk_sysfs_rate_store(pblk, buf, len);
-	else if (strcmp(attr->name, "gc_force") == 0)
+	if (strcmp(attr->name, "gc_force") == 0)
 		return pblk_sysfs_gc_force(pblk, buf, len);
 	else if (strcmp(attr->name, "max_sec_per_write") == 0)
 		return pblk_sysfs_set_sec_per_write(pblk, buf, len);