[v1] iommu/iova: Optimize iova_magazine_alloc()

[PATCH] iommu/iova: Optimize iova_magazine_alloc()

Posted by Zhen Lei 2 years, 8 months ago

Only the member 'size' needs to be initialized to 0. Clearing the array
pfns[], which is about 1 KiB in size, not only wastes time, but also
causes cache pollution.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 drivers/iommu/iova.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index fe452ce466429a7..c970b9a2819d7bb 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -647,7 +647,13 @@ struct iova_rcache {
 
 static struct iova_magazine *iova_magazine_alloc(gfp_t flags)
 {
-	return kzalloc(sizeof(struct iova_magazine), flags);
+	struct iova_magazine *mag;
+
+	mag = kmalloc(sizeof(struct iova_magazine), flags);
+	if (mag)
+		mag->size = 0;
+
+	return mag;
 }
 
 static void iova_magazine_free(struct iova_magazine *mag)
-- 
2.25.1

Re: [PATCH] iommu/iova: Optimize iova_magazine_alloc()

Posted by Robin Murphy 2 years, 8 months ago

On 2023-04-18 07:25, Zhen Lei wrote:
> Only the member 'size' needs to be initialized to 0. Clearing the array
> pfns[], which is about 1 KiB in size, not only wastes time, but also
> causes cache pollution.

Makes sense to me.

Acked-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>   drivers/iommu/iova.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index fe452ce466429a7..c970b9a2819d7bb 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -647,7 +647,13 @@ struct iova_rcache {
>   
>   static struct iova_magazine *iova_magazine_alloc(gfp_t flags)
>   {
> -	return kzalloc(sizeof(struct iova_magazine), flags);
> +	struct iova_magazine *mag;
> +
> +	mag = kmalloc(sizeof(struct iova_magazine), flags);

Nit: maybe sizeof(*mag) is preferable?

> +	if (mag)
> +		mag->size = 0;
> +
> +	return mag;
>   }
>   
>   static void iova_magazine_free(struct iova_magazine *mag)

Re: [PATCH] iommu/iova: Optimize iova_magazine_alloc()

Posted by Leizhen (ThunderTown) 2 years, 8 months ago


On 2023/4/20 18:38, Robin Murphy wrote:
> On 2023-04-18 07:25, Zhen Lei wrote:
>> Only the member 'size' needs to be initialized to 0. Clearing the array
>> pfns[], which is about 1 KiB in size, not only wastes time, but also
>> causes cache pollution.
> 
> Makes sense to me.
> 
> Acked-by: Robin Murphy <robin.murphy@arm.com>
> 
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>>   drivers/iommu/iova.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
>> index fe452ce466429a7..c970b9a2819d7bb 100644
>> --- a/drivers/iommu/iova.c
>> +++ b/drivers/iommu/iova.c
>> @@ -647,7 +647,13 @@ struct iova_rcache {
>>     static struct iova_magazine *iova_magazine_alloc(gfp_t flags)
>>   {
>> -    return kzalloc(sizeof(struct iova_magazine), flags);
>> +    struct iova_magazine *mag;
>> +
>> +    mag = kmalloc(sizeof(struct iova_magazine), flags);
> 
> Nit: maybe sizeof(*mag) is preferable?

Yes, sizeof(*mag) is the more recommended usage, I will post v2 tomorrow.

> 
>> +    if (mag)
>> +        mag->size = 0;
>> +
>> +    return mag;
>>   }
>>     static void iova_magazine_free(struct iova_magazine *mag)
> 
> .
> 

-- 
Regards,
  Zhen Lei

Re: [PATCH] iommu/iova: Optimize iova_magazine_alloc()

Posted by Joerg Roedel 2 years, 6 months ago

On Thu, Apr 20, 2023 at 07:52:14PM +0800, Leizhen (ThunderTown) wrote:
> Yes, sizeof(*mag) is the more recommended usage, I will post v2 tomorrow.

Somehow v2 didn't make it to my inbox, but I found it on lore. This is
applied now, thanks.

Regards,

	Joerg