[U-Boot] [U-BOOT] [PATCH] env: reduce the stack footprint for the env buf

[Wolfgang Denk]

Dear Lei Wen,

In message <AANLkTi=KNpJ02SHCp5FYqukYdMAXUN+LgVpK7O-6Veex at mail.gmail.com> you wrote:
> 
> The measurement is simple, for I don't change other part, the heap
> size and etc part
> size, but only move the temp buffer to the heap area instead of stack area.
> So this reduce the large memory need in the env_relocate_spec() function.
> So that the stack would not touch those memory since most function
> don't cost so much
> stack as env_relocate_spec() does...

You don't provide any real measurement results here.  Also, you did
not report what happens when you - for example - reduce the size of
your malloc arena by the size...

> The heap area is already enough for the env_relocate_spec() in our
> platform. Maybe
> you concern is for those platform don't allocate enough heap size for
> the env?...
> Also fragmentation problem I am not figure out clearly... Temporarily
> use large heap then free
> would make uboot unable to malloc enough memory in latter allocate?...

To sum it up:

- Your patch increases the code size, and the code complexity, and
  increases the risk of memory leaks.

- Your patch requires on many systems to increase the size of the
  malloc arena, with the result that the available memory at runtim
  becomes lower.

- Your patch fails to adjust the malloc arena size on the affected
  boards (and eventually any board may be affected, so all will have
  to be checked and verified).

- You claim that this patch helps to use less memory on your system,
  but you fail to prove this with actual numbers.


So we have a number of disadvantages for all users, a lot of effort
for all users (they all need to re-test their boards), and a claimed
but otherwise unproven advantage for a simgle user (you).

I hereby reject your patch.  If you really think it, you can still
maintain it as a local, out-of-tree patch.

Thanks.

Wolfgang Denk

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