Thanks a lot Mr. Ralf Baechle for Quick answer.
I will give more info.
mips 34kc is processor
and File we are using is arch/mips/include/asm/mach-generic/kmalloc.h
* Total overkill for most systems but need as a safe default.
* Set this one if any device in the system might do non-coherent DMA.
#define ARCH_KMALLOC_MINALIGN 128
#endif /* __ASM_MACH_GENERIC_KMALLOC_H */
So shall we make value ARCH_KMALLOC_MINALIGN from 128 to 32. is
there any problem ?
On Wed, Aug 18, 2010 at 7:03 PM, Ralf Baechle <firstname.lastname@example.org> wrote:
> On Wed, Aug 18, 2010 at 06:07:12PM +0530, naveen yadav wrote:
>> To: email@example.com, firstname.lastname@example.org
> Your sentences are to complex for majordomo to understand. Also its
> area of expertise is generally limited to mailing list related issues.
>> We are using MIPS(mips32r2) target. when I alloc memory using kmalloc
>> suppose 28 bytes, the kernel still consume 128 bytes.
>> So when I check File on kernel source mach-ip32/kmalloc.h
>> Since it is allign to 128 bytes so i understand that even if I
>> consume 1 byte it will waste 128 bytes.
>> #ifndef __ASM_MACH_IP32_KMALLOC_H
>> #define __ASM_MACH_IP32_KMALLOC_H
> Eh... That's an IP32-specific header. I have no idea why you're looking
> at it. It's not being used for your platform.
>> So I could not understand why it is allign to 128 bytes. Is there any
>> specific reason for it. ?
> Each allocation needs some memory for kmalloc's internal bookkeeping,
> the memory you actually asked for and for cacheline alignment. For very
> small allocations the later is likely to be larger than the other two
> so will be the deciding factor in actual memory allocation.
> The cacheline aligment results in better performance and on non-coherent
> platforms such as probably yours it is necessary to get get DMA transfers
> to work right.
> It would appear that in your case CONFIG_MIPS_L1_CACHE_SHIFT is set to 7.
> For a MIPS32-based platform (you didn' say what actual processor core!)
> that appears to be an excessively large number. 32 bytes would be a more
> typical figure. Just check the kernel bootup messages for the cacheline
> size if you don't know.