Preallocation of memory in 2.4 kernels

Preallocation of memory in 2.4 kernels

[chandrasekhar nagaraj]

Hi,
    We have a block driver which operates under heavy IO load.The driver 
always preallocates the memory for IO so that while IO is going ,it can take 
the required memory from the pool.(for performance reasons,we preallocate 
the memory).
But we do have some small chunks of memory allocation (say close to 4K) when 
the IO is in operation.(to update the stats,we require this memory).But 
under heavy load conditions,the kmalloc fails to get even this small chunk 
of data.
We felt that we could preallocate some 64K of memory pool(before the IO 
starts) and then when this kind of small memory request comes (note that 
this request size is variable) , we would use this memory pool instead of 
using the kmalloc.
Is there any mechanism in 2.4 kernels to achieve this task.?

Regards
Chandrasekhar

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Re: Preallocation of memory in 2.4 kernels

[Alan Cox]

On Gwe, 2004-08-13 at 19:11, chandrasekhar nagaraj wrote:
> We felt that we could preallocate some 64K of memory pool(before the IO 
> starts) and then when this kind of small memory request comes (note that 
> this request size is variable) , we would use this memory pool instead of 
> using the kmalloc.
> Is there any mechanism in 2.4 kernels to achieve this task.?

Yes - use kmalloc or multiple kmallocs before the I/O starts (eg
allocate in the driver startup). 2.6.x has a nice structure for doing
this and helpers but for the general case drivers just preallocate
buffers to be sure they can make progress. It's normally the most
efficient solution anyway.