* Re: [PATCH] bcache: remove the redundant judgment on bi_size
@ 2021-08-30 6:29 Xifengfei
2021-08-31 1:35 ` Coly Li
0 siblings, 1 reply; 6+ messages in thread
From: Xifengfei @ 2021-08-30 6:29 UTC (permalink / raw)
To: Coly Li; +Cc: linux-bcache, linux-kernel, kent.overstreet
（Sorry, there was an obvious typo in the last email）
Thanks a lot. I understand the purpose.
So is the original judgment process too complicated? Can we judge bi_size directly? This will be more concise
@@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
+ if (bio->bi_iter.bi_size)
i->sequential += bio->bi_iter.bi_size;
i->last = bio_end_sector(bio);
Thanks
Fengfei
-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de]
发送时间: 2021年8月29日 15:50
收件人: xifengfei (RD) <xi.fengfei@h3c.com>
抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org; kent.overstreet@gmail.com
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
On 8/29/21 12:49 PM, Fengfei Xi wrote:
> The bi_size is unsigned int type data not less than 0, so we can
> directly add bi_size without extra judgment
>
> Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
NACK. The check is necessary to avoid redundant and unnecessary memory write.
Coly Li
> ---
> drivers/md/bcache/request.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 6d1de889b..2788eec3a 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> - i->sequential += bio->bi_iter.bi_size;
> -
> + i->sequential += bio->bi_iter.bi_size;
> i->last = bio_end_sector(bio);
> i->jiffies = jiffies + msecs_to_jiffies(5000);
> task->sequential_io = i->sequential;
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] bcache: remove the redundant judgment on bi_size
2021-08-30 6:29 [PATCH] bcache: remove the redundant judgment on bi_size Xifengfei
@ 2021-08-31 1:35 ` Coly Li
0 siblings, 0 replies; 6+ messages in thread
From: Coly Li @ 2021-08-31 1:35 UTC (permalink / raw)
To: Xifengfei; +Cc: linux-bcache, linux-kernel, kent.overstreet
On 8/30/21 2:29 PM, Xifengfei wrote:
> （Sorry, there was an obvious typo in the last email）
> Thanks a lot. I understand the purpose.
> So is the original judgment process too complicated? Can we judge bi_size directly? This will be more concise
>
> @@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> + if (bio->bi_iter.bi_size)
> i->sequential += bio->bi_iter.bi_size;
>
> i->last = bio_end_sector(bio);
The above change works, but the code readability decreased because
how/why i->sequential is maintained is not that directly visible.
This is a difference of coding styles. IMHO for this particular case,
the readability is more important than less CPU instructions.
Thanks.
Coly Li
> Thanks
> Fengfei
>
> -----邮件原件-----
> 发件人: Coly Li [mailto:colyli@suse.de]
> 发送时间: 2021年8月29日 15:50
> 收件人: xifengfei (RD) <xi.fengfei@h3c.com>
> 抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org; kent.overstreet@gmail.com
> 主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
>
> On 8/29/21 12:49 PM, Fengfei Xi wrote:
>> The bi_size is unsigned int type data not less than 0, so we can
>> directly add bi_size without extra judgment
>>
>> Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
> NACK. The check is necessary to avoid redundant and unnecessary memory write.
>
> Coly Li
>
>> ---
>> drivers/md/bcache/request.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
>> index 6d1de889b..2788eec3a 100644
>> --- a/drivers/md/bcache/request.c
>> +++ b/drivers/md/bcache/request.c
>> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
>> add_sequential(task);
>> i->sequential = 0;
>> found:
>> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
>> - i->sequential += bio->bi_iter.bi_size;
>> -
>> + i->sequential += bio->bi_iter.bi_size;
>> i->last = bio_end_sector(bio);
>> i->jiffies = jiffies + msecs_to_jiffies(5000);
>> task->sequential_io = i->sequential;
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] bcache: remove the redundant judgment on bi_size
@ 2021-08-31 2:05 Xifengfei
0 siblings, 0 replies; 6+ messages in thread
From: Xifengfei @ 2021-08-31 2:05 UTC (permalink / raw)
To: Coly Li; +Cc: linux-bcache, linux-kernel, kent.overstreet
OK. Thanks for our explanation. ^_^
Feng fei
-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de]
发送时间: 2021年8月31日 9:35
收件人: xifengfei (RD) <xi.fengfei@h3c.com>
抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org; kent.overstreet@gmail.com
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
On 8/30/21 2:29 PM, Xifengfei wrote:
> （Sorry, there was an obvious typo in the last email）
> Thanks a lot. I understand the purpose.
> So is the original judgment process too complicated? Can we judge
> bi_size directly? This will be more concise
>
> @@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> + if (bio->bi_iter.bi_size)
> i->sequential += bio->bi_iter.bi_size;
>
> i->last = bio_end_sector(bio);
The above change works, but the code readability decreased because how/why i->sequential is maintained is not that directly visible.
This is a difference of coding styles. IMHO for this particular case, the readability is more important than less CPU instructions.
Thanks.
Coly Li
> Thanks
> Fengfei
>
> -----邮件原件-----
> 发件人: Coly Li [mailto:colyli@suse.de]
> 发送时间: 2021年8月29日 15:50
> 收件人: xifengfei (RD) <xi.fengfei@h3c.com>
> 抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org;
> kent.overstreet@gmail.com
> 主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
>
> On 8/29/21 12:49 PM, Fengfei Xi wrote:
>> The bi_size is unsigned int type data not less than 0, so we can
>> directly add bi_size without extra judgment
>>
>> Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
> NACK. The check is necessary to avoid redundant and unnecessary memory write.
>
> Coly Li
>
>> ---
>> drivers/md/bcache/request.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/md/bcache/request.c
>> b/drivers/md/bcache/request.c index 6d1de889b..2788eec3a 100644
>> --- a/drivers/md/bcache/request.c
>> +++ b/drivers/md/bcache/request.c
>> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
>> add_sequential(task);
>> i->sequential = 0;
>> found:
>> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
>> - i->sequential += bio->bi_iter.bi_size;
>> -
>> + i->sequential += bio->bi_iter.bi_size;
>> i->last = bio_end_sector(bio);
>> i->jiffies = jiffies + msecs_to_jiffies(5000);
>> task->sequential_io = i->sequential;
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] bcache: remove the redundant judgment on bi_size
@ 2021-08-30 6:23 Xifengfei
0 siblings, 0 replies; 6+ messages in thread
From: Xifengfei @ 2021-08-30 6:23 UTC (permalink / raw)
To: Coly Li; +Cc: linux-bcache, linux-kernel, kent.overstreet
Thanks a lot. I understand the purpose.
So is the original judgment process too complicated? Can we judge bi_size directly? This will be more concise
@@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
+ if (!bio->bi_iter.bi_size)
i->sequential += bio->bi_iter.bi_size;
i->last = bio_end_sector(bio);
Thanks
Fengfei
-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de]
发送时间: 2021年8月29日 15:50
收件人: xifengfei (RD) <xi.fengfei@h3c.com>
抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org; kent.overstreet@gmail.com
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
On 8/29/21 12:49 PM, Fengfei Xi wrote:
> The bi_size is unsigned int type data not less than 0, so we can
> directly add bi_size without extra judgment
>
> Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
NACK. The check is necessary to avoid redundant and unnecessary memory write.
Coly Li
> ---
> drivers/md/bcache/request.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 6d1de889b..2788eec3a 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> - i->sequential += bio->bi_iter.bi_size;
> -
> + i->sequential += bio->bi_iter.bi_size;
> i->last = bio_end_sector(bio);
> i->jiffies = jiffies + msecs_to_jiffies(5000);
> task->sequential_io = i->sequential;
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH] bcache: remove the redundant judgment on bi_size
@ 2021-08-29 4:49 Fengfei Xi
2021-08-29 7:49 ` Coly Li
0 siblings, 1 reply; 6+ messages in thread
From: Fengfei Xi @ 2021-08-29 4:49 UTC (permalink / raw)
To: colyli, kent.overstreet; +Cc: linux-bcache, linux-kernel, Fengfei Xi
The bi_size is unsigned int type data not less than 0,
so we can directly add bi_size without extra judgment
Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
---
drivers/md/bcache/request.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 6d1de889b..2788eec3a 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
- i->sequential += bio->bi_iter.bi_size;
-
+ i->sequential += bio->bi_iter.bi_size;
i->last = bio_end_sector(bio);
i->jiffies = jiffies + msecs_to_jiffies(5000);
task->sequential_io = i->sequential;
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] bcache: remove the redundant judgment on bi_size
2021-08-29 4:49 Fengfei Xi
@ 2021-08-29 7:49 ` Coly Li
0 siblings, 0 replies; 6+ messages in thread
From: Coly Li @ 2021-08-29 7:49 UTC (permalink / raw)
To: Fengfei Xi; +Cc: linux-bcache, linux-kernel, kent.overstreet
On 8/29/21 12:49 PM, Fengfei Xi wrote:
> The bi_size is unsigned int type data not less than 0,
> so we can directly add bi_size without extra judgment
>
> Signed-off-by: Fengfei Xi <xi.fengfei@h3c.com>
NACK. The check is necessary to avoid redundant and unnecessary memory
write.
Coly Li
> ---
> drivers/md/bcache/request.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 6d1de889b..2788eec3a 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> - i->sequential += bio->bi_iter.bi_size;
> -
> + i->sequential += bio->bi_iter.bi_size;
> i->last = bio_end_sector(bio);
> i->jiffies = jiffies + msecs_to_jiffies(5000);
> task->sequential_io = i->sequential;
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-08-31 2:05 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-08-30 6:29 [PATCH] bcache: remove the redundant judgment on bi_size Xifengfei
2021-08-31 1:35 ` Coly Li
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2021-08-31 2:05 Xifengfei
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2021-08-29 4:49 Fengfei Xi
2021-08-29 7:49 ` Coly Li
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