Problems in kernel memory allocation

[Sriram Narasimhan]

Hi,

I am having problems allocating more than 2.5 MB in the linux kernel.
I am using Linux 2.4.7-10 RH 7.2 on i386.

Physical RAM: 64 MB

I tried two methods of allocation, one using kmalloc and other using 
kmem_cache_alloc. Both of them failed to allocate more than 2.5 MB. 
(GFP_KERNEL / GFP_ATOMIC operations)
When I run 'free' I am able to see that the free physical memory is 
about 4MB and the free buffers/cache is about 52 MB.
The report is as follows:
           total       used       free     shared    buffers     cached
Mem:         62264      57928      4336          0       30152      17768
-/+ buffers/cache:       10008      52256
Swap:       192772          0     192772

I also found out that the /proc/meminfo had about 43MB of Inact_dirty . 
Is there any way to forcefully flush the dirty buffers ?
Why is the allocation consistently failing in about 2.5 or 3MB ?
Only when the free physical is about 30MB and I start allocating am I 
able to successfully allocate about 5MB.

Is there a restriction as to how much memory you can allocate in the 
kernel ?

Sriram