[alsa-devel] change kmalloc into vmalloc for large memory allocations

[Wang, Yalin]

Hi 


I find there is some drivers use kmalloc to allocate large 
Memorys during module_init,  some can be changed to use vmalloc
To save some low mem, I add log in kernel to track ,
And list them here:

https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/drivers/usb/gadget/f_mass_storage.c?h=master#n2724

https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/sound/soc/soc-core.c?h=master#n3772

https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/net/netfilter/nf_conntrack_ftp.c?h=master#n603
https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/net/netfilter/nf_conntrack_h323_main.c?h=master#n1849
https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/net/netfilter/nf_conntrack_irc.c?h=master#n247
https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/net/netfilter/nf_conntrack_sane.c?h=master#n195

https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/drivers/input/evdev.c?h=master#n403


they allocate large memory from 10k~64K , 
this will use lots of low mem, instead if we use 
vmalloc for these drivers , it will be good for some devices
like smart phone, we often encounter some errors like kmalloc failed 
because there is not enough low mem , especially when the device has physical 
memory less than 1GB .


could this module change the memory allocation into vmalloc ?

I was thinking that if we can introduce a helper function in kmalloc.h like this :

Kmalloc(size, flags)
{
	If (size > PAGE_SIZE && flags&CAN_USE_VMALLOC_FLAG)
		return vmalloc(size);
	Else
		return real_kmalloc(size);
}

Kfree(ptr)
{
	If (is_vmalloc_addr(ptr))
		Vfree(ptr);
	Else
		Kfree(ptr);
}


But we need add some flags to ensure always use kmalloc for
Some special use (dma etc..)

How do you think of it ?

Thanks