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lightnvm: pblk: set conservative threshold for user writes

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In a worst-case scenario (random writes), OP% of sectors
in each line will be invalid, and we will then need
to move data out of 100/OP% lines to free a single line.

So, to prevent the possibility of running out of lines,
temporarily block user writes when there is less than
100/OP% free lines.

Also ensure that pblk creation does not produce instances
with insufficient over provisioning.

Insufficient over-provising is not a problem on real hardware,
but often an issue when running QEMU simulations (with few lines).
100 lines is enough to create a sane instance with the standard
(11%) over provisioning.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Hans Holmberg
2018-12-11 20:16:13 +01:00
committed by Jens Axboe
parent 525f7bb2c9
commit 3bcebc5bac
3 changed files with 44 additions and 13 deletions
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40
drivers/lightnvm/pblk-init.c
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@@ -635,7 +635,7 @@ static unsigned int calc_emeta_len(struct pblk *pblk)
return (lm->emeta_len[1] + lm->emeta_len[2] + lm->emeta_len[3]);
}
static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
static int pblk_set_provision(struct pblk *pblk, int nr_free_chks)
{
struct nvm_tgt_dev *dev = pblk->dev;
struct pblk_line_mgmt *l_mg = &pblk->l_mg;
@@ -643,23 +643,41 @@ static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
struct nvm_geo *geo = &dev->geo;
sector_t provisioned;
int sec_meta, blk_meta;
int minimum;
if (geo->op == NVM_TARGET_DEFAULT_OP)
pblk->op = PBLK_DEFAULT_OP;
else
pblk->op = geo->op;
provisioned = nr_free_blks;
minimum = pblk_get_min_chks(pblk);
provisioned = nr_free_chks;
provisioned *= (100 - pblk->op);
sector_div(provisioned, 100);
pblk->op_blks = nr_free_blks - provisioned;
if ((nr_free_chks - provisioned) < minimum) {
if (geo->op != NVM_TARGET_DEFAULT_OP) {
pblk_err(pblk, "OP too small to create a sane instance\n");
return -EINTR;
}
/* If the user did not specify an OP value, and PBLK_DEFAULT_OP
* is not enough, calculate and set sane value
*/
provisioned = nr_free_chks - minimum;
pblk->op = (100 * minimum) / nr_free_chks;
pblk_info(pblk, "Default OP insufficient, adjusting OP to %d\n",
pblk->op);
}
pblk->op_blks = nr_free_chks - provisioned;
/* Internally pblk manages all free blocks, but all calculations based
* on user capacity consider only provisioned blocks
*/
pblk->rl.total_blocks = nr_free_blks;
pblk->rl.nr_secs = nr_free_blks * geo->clba;
pblk->rl.total_blocks = nr_free_chks;
pblk->rl.nr_secs = nr_free_chks * geo->clba;
/* Consider sectors used for metadata */
sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;
@@ -667,8 +685,10 @@ static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
pblk->capacity = (provisioned - blk_meta) * geo->clba;
atomic_set(&pblk->rl.free_blocks, nr_free_blks);
atomic_set(&pblk->rl.free_user_blocks, nr_free_blks);
atomic_set(&pblk->rl.free_blocks, nr_free_chks);
atomic_set(&pblk->rl.free_user_blocks, nr_free_chks);
return 0;
}
static int pblk_setup_line_meta_chk(struct pblk *pblk, struct pblk_line *line,
@@ -984,7 +1004,7 @@ static int pblk_lines_init(struct pblk *pblk)
struct pblk_line_mgmt *l_mg = &pblk->l_mg;
struct pblk_line *line;
void *chunk_meta;
long nr_free_chks = 0;
int nr_free_chks = 0;
int i, ret;
ret = pblk_line_meta_init(pblk);
@@ -1031,7 +1051,9 @@ static int pblk_lines_init(struct pblk *pblk)
goto fail_free_lines;
}
pblk_set_provision(pblk, nr_free_chks);
ret = pblk_set_provision(pblk, nr_free_chks);
if (ret)
goto fail_free_lines;
vfree(chunk_meta);
return 0;