2024-06-05 13:56:29

by cuitao

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

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 <[email protected]>
---
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

2024-06-06 00:29:59

by Jason Wang

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

On Wed, Jun 5, 2024 at 9:56 PM cuitao <[email protected]> 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 <[email protected]>
> ---
> 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

2024-06-06 07:18:58

by Michael S. Tsirkin

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

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 <[email protected]>
> ---
> 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

2024-06-06 07:25:42

by cuitao

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

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 <[email protected]>
>> ---
>> 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