[PATCH] pblk: fix max_io calculation

[PATCH] pblk: fix max_io calculation

[Javier González]

When calculating the maximun I/O size allowed into the buffer, consider
the write size (ws_opt) used by the write thread in order to cover the
case in which, due to flushes, the mem and subm pointers are disaligned
by (ws_opt - 1). This case currently translates into a stall when
an I/O of the largest possible size is submitted.

Fixes: f9f9d1ae2c66 ("lightnvm: pblk: prevent stall due to wb threshold")

Signed-off-by: Javier González <javier@javigon.com>
---

Matias: Can you apply this as a fix to 5.1. This is a case I missed when fixing
the wb threshold, which is also scheduled for 5.1

Thanks,
Javier

 drivers/lightnvm/pblk-rl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
index b014957dde0b..a5f8bc2defbc 100644
--- a/drivers/lightnvm/pblk-rl.c
+++ b/drivers/lightnvm/pblk-rl.c
@@ -233,10 +233,15 @@ void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)
 	/* To start with, all buffer is available to user I/O writers */
 	rl->rb_budget = budget;
 	rl->rb_user_max = budget;
-	rl->rb_max_io = threshold ? (budget - threshold) : (budget - 1);
 	rl->rb_gc_max = 0;
 	rl->rb_state = PBLK_RL_HIGH;
 
+	/* Maximize I/O size and ansure that back threshold is respected */
+	if (threshold)
+		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
+	else
+		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;
+
 	atomic_set(&rl->rb_user_cnt, 0);
 	atomic_set(&rl->rb_gc_cnt, 0);
 	atomic_set(&rl->rb_space, -1);
-- 
2.17.1

Re: [PATCH] pblk: fix max_io calculation

[Matias Bjørling]

On 3/7/19 1:18 PM, Javier González wrote:
> When calculating the maximun I/O size allowed into the buffer, consider
> the write size (ws_opt) used by the write thread in order to cover the
> case in which, due to flushes, the mem and subm pointers are disaligned
> by (ws_opt - 1). This case currently translates into a stall when
> an I/O of the largest possible size is submitted.
> 
> Fixes: f9f9d1ae2c66 ("lightnvm: pblk: prevent stall due to wb threshold")
> 
> Signed-off-by: Javier González <javier@javigon.com>
> ---
> 
> Matias: Can you apply this as a fix to 5.1. This is a case I missed when fixing
> the wb threshold, which is also scheduled for 5.1
> 
> Thanks,
> Javier
> 
>   drivers/lightnvm/pblk-rl.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
> index b014957dde0b..a5f8bc2defbc 100644
> --- a/drivers/lightnvm/pblk-rl.c
> +++ b/drivers/lightnvm/pblk-rl.c
> @@ -233,10 +233,15 @@ void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)
>   	/* To start with, all buffer is available to user I/O writers */
>   	rl->rb_budget = budget;
>   	rl->rb_user_max = budget;
> -	rl->rb_max_io = threshold ? (budget - threshold) : (budget - 1);
>   	rl->rb_gc_max = 0;
>   	rl->rb_state = PBLK_RL_HIGH;
>   
> +	/* Maximize I/O size and ansure that back threshold is respected */
> +	if (threshold)
> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
> +	else
> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;
> +
>   	atomic_set(&rl->rb_user_cnt, 0);
>   	atomic_set(&rl->rb_gc_cnt, 0);
>   	atomic_set(&rl->rb_space, -1);
> 

Hi Jens,

If possible, could you please pick this one up for 5.1? It fixes a 
previous patch that was introduced in 5.1 that should fix a stall, but 
didn't quite catch it.

Thank you,
-Matias

Re: [PATCH] pblk: fix max_io calculation

[Jens Axboe]

On 3/7/19 8:57 AM, Matias Bjørling wrote:
> On 3/7/19 1:18 PM, Javier González wrote:
>> When calculating the maximun I/O size allowed into the buffer, consider
>> the write size (ws_opt) used by the write thread in order to cover the
>> case in which, due to flushes, the mem and subm pointers are disaligned
>> by (ws_opt - 1). This case currently translates into a stall when
>> an I/O of the largest possible size is submitted.
>>
>> Fixes: f9f9d1ae2c66 ("lightnvm: pblk: prevent stall due to wb threshold")
>>
>> Signed-off-by: Javier González <javier@javigon.com>
>> ---
>>
>> Matias: Can you apply this as a fix to 5.1. This is a case I missed when fixing
>> the wb threshold, which is also scheduled for 5.1
>>
>> Thanks,
>> Javier
>>
>>   drivers/lightnvm/pblk-rl.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
>> index b014957dde0b..a5f8bc2defbc 100644
>> --- a/drivers/lightnvm/pblk-rl.c
>> +++ b/drivers/lightnvm/pblk-rl.c
>> @@ -233,10 +233,15 @@ void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)
>>   	/* To start with, all buffer is available to user I/O writers */
>>   	rl->rb_budget = budget;
>>   	rl->rb_user_max = budget;
>> -	rl->rb_max_io = threshold ? (budget - threshold) : (budget - 1);
>>   	rl->rb_gc_max = 0;
>>   	rl->rb_state = PBLK_RL_HIGH;
>>   
>> +	/* Maximize I/O size and ansure that back threshold is respected */
>> +	if (threshold)
>> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
>> +	else
>> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;
>> +
>>   	atomic_set(&rl->rb_user_cnt, 0);
>>   	atomic_set(&rl->rb_gc_cnt, 0);
>>   	atomic_set(&rl->rb_space, -1);
>>
> 
> Hi Jens,
> 
> If possible, could you please pick this one up for 5.1? It fixes a 
> previous patch that was introduced in 5.1 that should fix a stall, but 
> didn't quite catch it.

Applied

-- 
Jens Axboe