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

[Takashi Iwai]

At Fri, 28 Feb 2014 16:15:23 +0800,
Wang, Yalin wrote:
> 
> 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

At least the ASoC runtime case doesn't use the allocated memory as
buffer, and they are allocated only once per device, thus it shouldn't
be the problem you stated.  If it really consumes so much memory, we
need to rethink, instead of allocating an array but allocate each
object, for example.


thanks,

Takashi


> 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
> 
> 
>