[U-Boot] [PATCH] malloc_simple: Add simple malloc free function

[Chin Liang See <clsee@altera.com>]

On Wed, 2016-08-03 at 09:53 +0200, Marek Vasut wrote:
> On 08/03/2016 09:30 AM, Chin Liang See wrote:
> > Hi Marek,
> 
> Hi,
> 
> > On Wed, 2016-08-03 at 08:58 +0200, Marek Vasut wrote:
> > > On 08/03/2016 05:24 AM, Chin Liang See wrote:
> > > > Enable a simple malloc implementation which will minimize
> > > > memory usage prior relocation. This is essential as memory
> > > > available prior location is internal memory and limited in
> > > > size.
> > > > 
> > > > This implementation will stored last 2 usage of malloc. When
> > > > free is invoked and the free address matched, we shall revert
> > > > to previous value of gd->malloc_ptr that we stored.
> > > 
> > > This looks unnecessarily convoluted and fragile design.
> > > What problem do you observe and on what platform ?
> > 
> > Actually this for our Arria10 SoC device. In order to get DDR
> > working,
> > we need to program FPGA. To improve the usability, we put the FPGA
> > programming file (RBF) into FAT partition.
> > 
> > In that sense, we would need to use FAT driver prior relocation /
> > DDR
> > available. Due to that, the malloc usage is high and memory
> > available
> > is limited prior DDR available. 
> 
> I was under the impression that you have 256kiB of SRAM on the A10.
> SPL should consume about 64 kiB tops, including support for loading
> from VFAT. So you have 192 kiB available, how is that not enough ?

But I presume we won't want to limit that minimum 256MB of internal
memory needed for simple malloc usage, right?

> 
> > The simple malloc helps but without the free, its consumed way too
> > much
> > memory than saving. Hence this simple malloc free patch help. So I
> > believe this would benefits those who are executing complex
> > operation
> > prior relocation :) 
> 
> I believe you need to identify who is calling malloc() to obtain big
> buffers without recycling them.
> 

It's the fat driver which is utilizing the malloc.

> Your design breaks in the scenario where someone does big malloc
> followed by two small mallocs if I understand it correctly. This
> doesn't scale and is a hack.
> 

Actually the proposed free is a simple implementation which acts as
stack push and pop with depth of 2. This is to enhance existing
implementation which don't handle the pop. This get worst especially
dealing with fat driver.

Thanks
Chin Liang

> > Thanks
> > Chin Liang
> > 
> 
>