[PATCH v2 0/2] Fix and cleanup some comments in blk-wbt

[PATCH v2 0/2] Fix and cleanup some comments in blk-wbt

[Tang Yizhou]

From: Tang Yizhou <yizhou.tang@shopee.com>

v2: Take Yuai's advice. Modify the subject of patch #1. Move the
modifications to the comments for wb_timer_fn to patch #2.

Tang Yizhou (2):
  blk-wbt: Fix some comments
  blk-wbt: Cleanup a comment in wb_timer_fn

 block/blk-wbt.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

-- 
2.25.1

[PATCH v2 1/2] blk-wbt: Fix some comments

[Tang Yizhou]

From: Tang Yizhou <yizhou.tang@shopee.com>

wbt_wait() no longer uses a spinlock as a parameter. Update the function
comments accordingly.

RWB_UNKNOWN_BUMP is used when we gradually adjust scale_steps toward the
center state, which is a value of 0.

Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
---
 block/blk-wbt.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 6dfc659d22e2..8b73c0c11aec 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -136,8 +136,9 @@ enum {
 	RWB_MIN_WRITE_SAMPLES	= 3,
 
 	/*
-	 * If we have this number of consecutive windows with not enough
-	 * information to scale up or down, scale up.
+	 * If we have this number of consecutive windows without enough
+	 * information to scale up or down, slowly return to center state
+	 * (step == 0).
 	 */
 	RWB_UNKNOWN_BUMP	= 5,
 };
@@ -638,11 +639,7 @@ static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
 	__wbt_done(rqos, flags);
 }
 
-/*
- * May sleep, if we have exceeded the writeback limits. Caller can pass
- * in an irq held spinlock, if it holds one when calling this function.
- * If we do sleep, we'll release and re-grab it.
- */
+/* May sleep, if we have exceeded the writeback limits. */
 static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
 {
 	struct rq_wb *rwb = RQWB(rqos);
-- 
2.25.1

[PATCH v2 2/2] blk-wbt: Cleanup a comment in wb_timer_fn

[Tang Yizhou]

From: Tang Yizhou <yizhou.tang@shopee.com>

The original comment contains a grammatical error. Rewrite it into a more
easily understandable sentence.

Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
---
 block/blk-wbt.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 8b73c0c11aec..f1754d07f7e0 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -447,9 +447,9 @@ static void wb_timer_fn(struct blk_stat_callback *cb)
 		break;
 	case LAT_UNKNOWN_WRITES:
 		/*
-		 * We started a the center step, but don't have a valid
-		 * read/write sample, but we do have writes going on.
-		 * Allow step to go negative, to increase write perf.
+		 * We don't have a valid read/write sample, but we do have
+		 * writes going on. Allow step to go negative, to increase
+		 * write performance.
 		 */
 		scale_up(rwb);
 		break;
-- 
2.25.1

Re: [PATCH v2 1/2] blk-wbt: Fix some comments

[Yu Kuai]

Hi,

在 2025/02/13 18:06, Tang Yizhou 写道:
> From: Tang Yizhou <yizhou.tang@shopee.com>
> 
> wbt_wait() no longer uses a spinlock as a parameter. Update the function
> comments accordingly.
> 
> RWB_UNKNOWN_BUMP is used when we gradually adjust scale_steps toward the
> center state, which is a value of 0.
> 
> Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
> ---
>   block/blk-wbt.c | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
> 

LGTM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>

> diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> index 6dfc659d22e2..8b73c0c11aec 100644
> --- a/block/blk-wbt.c
> +++ b/block/blk-wbt.c
> @@ -136,8 +136,9 @@ enum {
>   	RWB_MIN_WRITE_SAMPLES	= 3,
>   
>   	/*
> -	 * If we have this number of consecutive windows with not enough
> -	 * information to scale up or down, scale up.
> +	 * If we have this number of consecutive windows without enough
> +	 * information to scale up or down, slowly return to center state
> +	 * (step == 0).
>   	 */
>   	RWB_UNKNOWN_BUMP	= 5,
>   };
> @@ -638,11 +639,7 @@ static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
>   	__wbt_done(rqos, flags);
>   }
>   
> -/*
> - * May sleep, if we have exceeded the writeback limits. Caller can pass
> - * in an irq held spinlock, if it holds one when calling this function.
> - * If we do sleep, we'll release and re-grab it.
> - */
> +/* May sleep, if we have exceeded the writeback limits. */
>   static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
>   {
>   	struct rq_wb *rwb = RQWB(rqos);
> 

Re: [PATCH v2 2/2] blk-wbt: Cleanup a comment in wb_timer_fn

[Yu Kuai]

Hi,

在 2025/02/13 18:06, Tang Yizhou 写道:
> From: Tang Yizhou <yizhou.tang@shopee.com>
> 
> The original comment contains a grammatical error. Rewrite it into a more
> easily understandable sentence.
> 
> Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
> ---
>   block/blk-wbt.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 

Personally, I don't think this patch is necessary, people can still
understand with this error. I'm not expecting a seperate patch :(

Thanks,
Kuai

> diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> index 8b73c0c11aec..f1754d07f7e0 100644
> --- a/block/blk-wbt.c
> +++ b/block/blk-wbt.c
> @@ -447,9 +447,9 @@ static void wb_timer_fn(struct blk_stat_callback *cb)
>   		break;
>   	case LAT_UNKNOWN_WRITES:
>   		/*
> -		 * We started a the center step, but don't have a valid
> -		 * read/write sample, but we do have writes going on.
> -		 * Allow step to go negative, to increase write perf.
> +		 * We don't have a valid read/write sample, but we do have
> +		 * writes going on. Allow step to go negative, to increase
> +		 * write performance.
>   		 */
>   		scale_up(rwb);
>   		break;
> 

Re: [PATCH v2 2/2] blk-wbt: Cleanup a comment in wb_timer_fn

[Tang Yizhou]

On Thu, Feb 13, 2025 at 7:17 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>
> Hi,
>
> 在 2025/02/13 18:06, Tang Yizhou 写道:
> > From: Tang Yizhou <yizhou.tang@shopee.com>
> >
> > The original comment contains a grammatical error. Rewrite it into a more
> > easily understandable sentence.
> >
> > Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
> > ---
> >   block/blk-wbt.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
>
> Personally, I don't think this patch is necessary, people can still
> understand with this error. I'm not expecting a seperate patch :(
>
> Thanks,
> Kuai
>

Got it. Let's see if others have any suggestions.

Thanks,
Yi

> > diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> > index 8b73c0c11aec..f1754d07f7e0 100644
> > --- a/block/blk-wbt.c
> > +++ b/block/blk-wbt.c
> > @@ -447,9 +447,9 @@ static void wb_timer_fn(struct blk_stat_callback *cb)
> >               break;
> >       case LAT_UNKNOWN_WRITES:
> >               /*
> > -              * We started a the center step, but don't have a valid
> > -              * read/write sample, but we do have writes going on.
> > -              * Allow step to go negative, to increase write perf.
> > +              * We don't have a valid read/write sample, but we do have
> > +              * writes going on. Allow step to go negative, to increase
> > +              * write performance.
> >                */
> >               scale_up(rwb);
> >               break;
> >
>

Re: [PATCH v2 1/2] blk-wbt: Fix some comments

[Yizhou Tang]

On Thu, Feb 13, 2025 at 7:06 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>
> Hi,
>
> 在 2025/02/13 18:06, Tang Yizhou 写道:
> > From: Tang Yizhou <yizhou.tang@shopee.com>
> >
> > wbt_wait() no longer uses a spinlock as a parameter. Update the function
> > comments accordingly.
> >
> > RWB_UNKNOWN_BUMP is used when we gradually adjust scale_steps toward the
> > center state, which is a value of 0.
> >
> > Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
> > ---
> >   block/blk-wbt.c | 11 ++++-------
> >   1 file changed, 4 insertions(+), 7 deletions(-)
> >
>
> LGTM
> Reviewed-by: Yu Kuai <yukuai3@huawei.com>

Hi Jens, could you kindly review and consider merging this patch?

Yi.

>
> > diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> > index 6dfc659d22e2..8b73c0c11aec 100644
> > --- a/block/blk-wbt.c
> > +++ b/block/blk-wbt.c
> > @@ -136,8 +136,9 @@ enum {
> >       RWB_MIN_WRITE_SAMPLES   = 3,
> >
> >       /*
> > -      * If we have this number of consecutive windows with not enough
> > -      * information to scale up or down, scale up.
> > +      * If we have this number of consecutive windows without enough
> > +      * information to scale up or down, slowly return to center state
> > +      * (step == 0).
> >        */
> >       RWB_UNKNOWN_BUMP        = 5,
> >   };
> > @@ -638,11 +639,7 @@ static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
> >       __wbt_done(rqos, flags);
> >   }
> >
> > -/*
> > - * May sleep, if we have exceeded the writeback limits. Caller can pass
> > - * in an irq held spinlock, if it holds one when calling this function.
> > - * If we do sleep, we'll release and re-grab it.
> > - */
> > +/* May sleep, if we have exceeded the writeback limits. */
> >   static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
> >   {
> >       struct rq_wb *rwb = RQWB(rqos);
> >
>
>

Re: [PATCH v2 0/2] Fix and cleanup some comments in blk-wbt

[Jens Axboe]

On Thu, 13 Feb 2025 18:06:09 +0800, Tang Yizhou wrote:
> v2: Take Yuai's advice. Modify the subject of patch #1. Move the
> modifications to the comments for wb_timer_fn to patch #2.
> 
> Tang Yizhou (2):
>   blk-wbt: Fix some comments
>   blk-wbt: Cleanup a comment in wb_timer_fn
> 
> [...]

Applied, thanks!

[1/2] blk-wbt: Fix some comments
      commit: 5d01d2df85f01ce083e0372bd3bd4968155e2911
[2/2] blk-wbt: Cleanup a comment in wb_timer_fn
      commit: 8ac17e6ae1bf4625b8fa457f135865c1fd86beae

Best regards,
-- 
Jens Axboe