[PATCH] tools/virtio: Use the __GFP_ZERO flag of kmalloc to complete the memory initialization.

[PATCH] tools/virtio: Use the __GFP_ZERO flag of kmalloc to complete the memory initialization.

[cuitao]

Use the __GFP_ZERO flag of kmalloc to initialize memory while allocating it,
without the need for an additional memset call.

Signed-off-by: cuitao <cuitao@kylinos.cn>
---
 tools/virtio/linux/kernel.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
index 6702008f7f5c..9e401fb7c215 100644
--- a/tools/virtio/linux/kernel.h
+++ b/tools/virtio/linux/kernel.h
@@ -66,10 +66,7 @@ static inline void *kmalloc_array(unsigned n, size_t s, gfp_t gfp)
 
 static inline void *kzalloc(size_t s, gfp_t gfp)
 {
-	void *p = kmalloc(s, gfp);
-
-	memset(p, 0, s);
-	return p;
+	return kmalloc(s, gfp | __GFP_ZERO);
 }
 
 static inline void *alloc_pages_exact(size_t s, gfp_t gfp)
-- 
2.25.1

Re: [PATCH] tools/virtio: Use the __GFP_ZERO flag of kmalloc to complete the memory initialization.

[Jason Wang]

On Wed, Jun 5, 2024 at 9:56 PM cuitao <cuitao@kylinos.cn> wrote:
>
> Use the __GFP_ZERO flag of kmalloc to initialize memory while allocating it,
> without the need for an additional memset call.
>
> Signed-off-by: cuitao <cuitao@kylinos.cn>
> ---
>  tools/virtio/linux/kernel.h | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
> index 6702008f7f5c..9e401fb7c215 100644
> --- a/tools/virtio/linux/kernel.h
> +++ b/tools/virtio/linux/kernel.h
> @@ -66,10 +66,7 @@ static inline void *kmalloc_array(unsigned n, size_t s, gfp_t gfp)
>
>  static inline void *kzalloc(size_t s, gfp_t gfp)
>  {
> -       void *p = kmalloc(s, gfp);
> -
> -       memset(p, 0, s);
> -       return p;
> +       return kmalloc(s, gfp | __GFP_ZERO);
>  }
>
>  static inline void *alloc_pages_exact(size_t s, gfp_t gfp)
> --
> 2.25.1
>

Does this really work?

extern void *__kmalloc_fake, *__kfree_ignore_start, *__kfree_ignore_end;
static inline void *kmalloc(size_t s, gfp_t gfp)
{
  if (__kmalloc_fake)
                return __kmalloc_fake;
        return malloc(s);
}

Thanks

Re: [PATCH] tools/virtio: Use the __GFP_ZERO flag of kmalloc to complete the memory initialization.

[Michael S. Tsirkin]

On Wed, Jun 05, 2024 at 09:52:45PM +0800, cuitao wrote:
> Use the __GFP_ZERO flag of kmalloc to initialize memory while allocating it,
> without the need for an additional memset call.
> 
> Signed-off-by: cuitao <cuitao@kylinos.cn>
> ---
>  tools/virtio/linux/kernel.h | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
> index 6702008f7f5c..9e401fb7c215 100644
> --- a/tools/virtio/linux/kernel.h
> +++ b/tools/virtio/linux/kernel.h
> @@ -66,10 +66,7 @@ static inline void *kmalloc_array(unsigned n, size_t s, gfp_t gfp)
>  
>  static inline void *kzalloc(size_t s, gfp_t gfp)
>  {
> -	void *p = kmalloc(s, gfp);
> -
> -	memset(p, 0, s);
> -	return p;
> +	return kmalloc(s, gfp | __GFP_ZERO);
>  }


Why do we care? It's just here to make things compile. The simpler the
better.

>  static inline void *alloc_pages_exact(size_t s, gfp_t gfp)
> -- 
> 2.25.1

Re: [PATCH] tools/virtio: Use the __GFP_ZERO flag of kmalloc to complete the memory initialization.

[cuitao]

Sorry, maybe I'm wrong.

I wonder if the gfp parameter in static inline void *kmalloc(size_t s, 
gfp_t gfp) can be deleted if it is not used.

Or would be better to move memset to kmalloc.

Like this:
#define __GFP_ZERO 0x1
static inline void *kmalloc(size_t s, gfp_t gfp)
{
     void *p;
     if (__kmalloc_fake)
         return __kmalloc_fake;

     p = malloc(s);
     if (!p)
             return p;

     if (gfp & __GFP_ZERO)
         memset(p, 0, s);
     return p;
}

在 2024/6/6 15:18, Michael S. Tsirkin 写道:
> On Wed, Jun 05, 2024 at 09:52:45PM +0800, cuitao wrote:
>> Use the __GFP_ZERO flag of kmalloc to initialize memory while allocating it,
>> without the need for an additional memset call.
>>
>> Signed-off-by: cuitao <cuitao@kylinos.cn>
>> ---
>>   tools/virtio/linux/kernel.h | 5 +----
>>   1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
>> index 6702008f7f5c..9e401fb7c215 100644
>> --- a/tools/virtio/linux/kernel.h
>> +++ b/tools/virtio/linux/kernel.h
>> @@ -66,10 +66,7 @@ static inline void *kmalloc_array(unsigned n, size_t s, gfp_t gfp)
>>   
>>   static inline void *kzalloc(size_t s, gfp_t gfp)
>>   {
>> -	void *p = kmalloc(s, gfp);
>> -
>> -	memset(p, 0, s);
>> -	return p;
>> +	return kmalloc(s, gfp | __GFP_ZERO);
>>   }
>
> Why do we care? It's just here to make things compile. The simpler the
> better.
>
>>   static inline void *alloc_pages_exact(size_t s, gfp_t gfp)
>> -- 
>> 2.25.1