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lightnvm: pblk: enable 1 LUN configuration

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Metadata I/Os are scheduled to minimize their impact on user data I/Os.
When there are enough LUNs instantiated (i.e., enough bandwidth), it is
easy to interleave metadata and data one after the other so that
metadata I/Os are the ones being blocked and not vice-versa.

We do this by calculating the distance between the I/Os in terms of the
LUNs that are not in used, and selecting a free LUN that satisfies a
the simple heuristic that metadata is scheduled behind. The per-LUN
semaphores guarantee consistency. This works fine on >1 LUN
configuration. However, when a single LUN is instantiated, this design
leads to a deadlock, where metadata waits to be scheduled on a free LUN.

This patch implements the 1 LUN case by simply scheduling the metadada
I/O after the data I/O. In the process, we refactor the way a line is
replaced to ensure that metadata writes are submitted after data writes
in order to guarantee block sequentiality. Note that, since there is
only one LUN, both I/Os will block each other by design. However, such
configuration only pursues tight read latencies, not write bandwidth.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Javier González 2017-10-13 14:46:26 +02:00 • committed by Jens Axboe
parent 1e82123da6
commit 21d2287119
4 changed files with 29 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
drivers/lightnvm/pblk-core.c
View file

@ -1372,17 +1372,17 @@ void pblk_pipeline_stop(struct pblk *pblk)
spin_unlock(&l_mg->free_lock);
}
void pblk_line_replace_data(struct pblk *pblk)
struct pblk_line *pblk_line_replace_data(struct pblk *pblk)
{
struct pblk_line_mgmt *l_mg = &pblk->l_mg;
struct pblk_line *cur, *new;
struct pblk_line *cur, *new = NULL;
unsigned int left_seblks;
int is_next = 0;
cur = l_mg->data_line;
new = l_mg->data_next;
if (!new)
return;
goto out;
l_mg->data_line = new;
spin_lock(&l_mg->free_lock);
@ -1390,7 +1390,7 @@ void pblk_line_replace_data(struct pblk *pblk)
l_mg->data_line = NULL;
l_mg->data_next = NULL;
spin_unlock(&l_mg->free_lock);
return;
goto out;
}
pblk_line_setup_metadata(new, l_mg, &pblk->lm);
@ -1402,7 +1402,7 @@ retry_erase:
/* If line is not fully erased, erase it */
if (atomic_read(&new->left_eblks)) {
if (pblk_line_erase(pblk, new))
return;
goto out;
} else {
io_schedule();
}
@ -1413,7 +1413,7 @@ retry_setup:
if (!pblk_line_init_metadata(pblk, new, cur)) {
new = pblk_line_retry(pblk, new);
if (!new)
return;
goto out;
goto retry_setup;
}
@ -1421,7 +1421,7 @@ retry_setup:
if (!pblk_line_init_bb(pblk, new, 1)) {
new = pblk_line_retry(pblk, new);
if (!new)
return;
goto out;
goto retry_setup;
}
@ -1445,6 +1445,9 @@ retry_setup:
if (is_next)
pblk_rl_free_lines_dec(&pblk->rl, l_mg->data_next);
out:
return new;
}
void pblk_line_free(struct pblk *pblk, struct pblk_line *line)

8
drivers/lightnvm/pblk-init.c
View file

@ -711,8 +711,12 @@ add_emeta_page:
}
lm->emeta_bb = geo->nr_luns - i;
lm->min_blk_line = 1 + DIV_ROUND_UP(lm->smeta_sec + lm->emeta_sec[0],
geo->sec_per_blk);
lm->min_blk_line = 1;
if (geo->nr_luns > 1)
lm->min_blk_line += DIV_ROUND_UP(lm->smeta_sec +
lm->emeta_sec[0], geo->sec_per_blk);
if (lm->min_blk_line > lm->blk_per_line) {
pr_err("pblk: config. not supported. Min. LUN in line:%d\n",
lm->blk_per_line);

21
drivers/lightnvm/pblk-map.c
View file

@ -25,13 +25,23 @@ static void pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
unsigned int valid_secs)
{
struct pblk_line *line = pblk_line_get_data(pblk);
struct pblk_emeta *emeta = line->emeta;
struct pblk_emeta *emeta;
struct pblk_w_ctx *w_ctx;
__le64 *lba_list = emeta_to_lbas(pblk, emeta->buf);
__le64 *lba_list;
u64 paddr;
int nr_secs = pblk->min_write_pgs;
int i;
if (pblk_line_is_full(line)) {
struct pblk_line *prev_line = line;
line = pblk_line_replace_data(pblk);
pblk_line_close_meta(pblk, prev_line);
}
emeta = line->emeta;
lba_list = emeta_to_lbas(pblk, emeta->buf);
paddr = pblk_alloc_page(pblk, line, nr_secs);
for (i = 0; i < nr_secs; i++, paddr++) {
@ -60,13 +70,6 @@ static void pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
}
}
if (pblk_line_is_full(line)) {
struct pblk_line *prev_line = line;
pblk_line_replace_data(pblk);
pblk_line_close_meta(pblk, prev_line);
}
pblk_down_rq(pblk, ppa_list, nr_secs, lun_bitmap);
}

2
drivers/lightnvm/pblk.h
View file

@ -719,7 +719,7 @@ struct bio *pblk_bio_map_addr(struct pblk *pblk, void *data,
int alloc_type, gfp_t gfp_mask);
struct pblk_line *pblk_line_get(struct pblk *pblk);
struct pblk_line *pblk_line_get_first_data(struct pblk *pblk);
void pblk_line_replace_data(struct pblk *pblk);
struct pblk_line *pblk_line_replace_data(struct pblk *pblk);
int pblk_line_recov_alloc(struct pblk *pblk, struct pblk_line *line);
void pblk_line_recov_close(struct pblk *pblk, struct pblk_line *line);
struct pblk_line *pblk_line_get_data(struct pblk *pblk);