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

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Date:	Thu, 5 May 2016 10:02:59 +0000
From:	Javier González <javier@...xlabs.com>
To:	Matias Bjørling <mb@...htnvm.io>
CC:	Javier González <jg@...htnvm.io>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [PATCH 4/4] lightnvm: Precalculate max/min sectors per req.


> On 05 May 2016, at 11:54, Matias Bjørling <mb@...htnvm.io> wrote:
> 
>> On 05/04/2016 05:31 PM, Javier González 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 González <javier@...xlabs.com>
>> ---
>>  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.

Yes, you're right. Let us wait until we can communicate everything to the target. 

Thanks!
Javier