Re: malloc memory to be 32 byte aligned in kernel
On Tue, 28 Jan 2014 17:00:13 -0800, m silverstri said: > Thanks. How big should be my slab cache and how to allocate from that? kmem_cache_alloc() and kmem_cache_free() are your friends. > And to declare a struct ' __attribute__(aligned(32))'', does that mean > I do that for every file in my struct? I'm guessing you mean "for every field in my struct". And the answer is no, unless you actually need the alignment/padding for every field. You declare the struct wrapping all the stuff you need and give that the aligned(). pgp_sIBDY0rsj.pgp Description: PGP signature ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: malloc memory to be 32 byte aligned in kernel
Thanks. How big should be my slab cache and how to allocate from that?
And to declare a struct ' __attribute__(aligned(32))'', does that mean
I do that for every file in my struct?
On Tue, Jan 28, 2014 at 4:15 PM, wrote:
> On Tue, 28 Jan 2014 15:32:37 -0800, anish singh said:
>> On Tue, Jan 28, 2014 at 11:20 AM, m silverstri
>> wrote:
>> > Hi,
>> >
>> > I am writing a kernel driver, can you please tell me how can I
>> > allocate a buffer which is 32 byte aligned?
>> malloc already aligns memory for basic data types AFAIK
>
> Yes, but even if it allocates on a long-long boundary, he can still get
> hosed if it ends up on a 8-byte boundary that's *not* a 32-byte aligned.
>
> Your best approach is probably to use the KMEM_CACHE() macro to create a slab
> cache, and then allocate from that slab. See include/linux/slab.h
>
> /*
> * Please use this macro to create slab caches. Simply specify the
> * name of the structure and maybe some flags that are listed above.
> *
> * The alignment of the struct determines object alignment. If you
> * f.e. add cacheline_aligned_in_smp to the struct declaration
> * then the objects will be properly aligned in SMP configurations.
> */
> #define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,
> sizeof(struct __struct), __alignof__(struct __struct),
> (__flags), NULL)
>
> Oh, and you'll need to declare a 'struct foo {...} __attribute__(aligned(32))'
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Re: malloc memory to be 32 byte aligned in kernel
On Tue, 28 Jan 2014 15:32:37 -0800, anish singh said:
> On Tue, Jan 28, 2014 at 11:20 AM, m silverstri
> wrote:
> > Hi,
> >
> > I am writing a kernel driver, can you please tell me how can I
> > allocate a buffer which is 32 byte aligned?
> malloc already aligns memory for basic data types AFAIK
Yes, but even if it allocates on a long-long boundary, he can still get
hosed if it ends up on a 8-byte boundary that's *not* a 32-byte aligned.
Your best approach is probably to use the KMEM_CACHE() macro to create a slab
cache, and then allocate from that slab. See include/linux/slab.h
/*
* Please use this macro to create slab caches. Simply specify the
* name of the structure and maybe some flags that are listed above.
*
* The alignment of the struct determines object alignment. If you
* f.e. add cacheline_aligned_in_smp to the struct declaration
* then the objects will be properly aligned in SMP configurations.
*/
#define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,
sizeof(struct __struct), __alignof__(struct __struct),
(__flags), NULL)
Oh, and you'll need to declare a 'struct foo {...} __attribute__(aligned(32))'
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Re: malloc memory to be 32 byte aligned in kernel
On Tue, Jan 28, 2014 at 11:20 AM, m silverstri wrote: > Hi, > > I am writing a kernel driver, can you please tell me how can I > allocate a buffer which is 32 byte aligned? malloc already aligns memory for basic data types AFAIK > > Thank you. > > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
malloc memory to be 32 byte aligned in kernel
Hi, I am writing a kernel driver, can you please tell me how can I allocate a buffer which is 32 byte aligned? Thank you. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
