Re: [PATCH 4/4] lightnvm: Precalculate max/min sectors per req.

From: Matias BjÃrling
Date: Thu May 05 2016 - 05:54:30 EST


On 05/04/2016 05:31 PM, Javier GonzÃlez wrote:
Add two precalculated values to nvm_rq: (i) maximum number of sectors
per general request; and (ii) minimum number of sectors per write
request.

Signed-off-by: Javier GonzÃlez <javier@xxxxxxxxxxxx>
---
drivers/lightnvm/core.c | 3 +++
include/linux/lightnvm.h | 4 +++-
2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index 4cd9803..85682d91 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -573,6 +573,9 @@ static int nvm_core_init(struct nvm_dev *dev)

dev->plane_mode = NVM_PLANE_SINGLE;
dev->max_rq_size = dev->ops->max_phys_sect * dev->sec_size;
+ dev->max_sec_rq = dev->ops->max_phys_sect;
+ /* assume max_phys_sect % dev->min_write_pgs == 0 */
+ dev->min_sec_w_rq = dev->sec_per_pl * (dev->sec_size / PAGE_SIZE);

if (grp->mpos & 0x020202)
dev->plane_mode = NVM_PLANE_DOUBLE;
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index 67e72f5..c2dfd0c 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -351,7 +351,9 @@ struct nvm_dev {
/* Calculated/Cached values. These do not reflect the actual usable
* blocks at run-time.
*/
- int max_rq_size;
+ int max_rq_size; /* maximum size of a single request */
+ int max_sec_rq; /* maximum amount of sectors that fit in one req. */
+ int min_sec_w_rq; /* minimum amount of sectors required on write req. */
int plane_mode; /* drive device in single, double or quad mode */

int sec_per_pl; /* all sectors across planes */


I think this is best kept within pblk for now. The min_sec_w_rq is not enough to describe the pages to be written. It must also follow a specific order, which is not communicated only with minimum page writes.