[U-Boot] [PATCH 0/3] arm: reduce .bss section clear time

Stefan Roese
2015-01-28T13:12:04Z

Hi Przemyslaw,

On 28.01.2015 13:55, Przemyslaw Marczak wrote:
> This patchset reduces the boot time for ARM architecture,
> Exynos boards, and boards with DFU enabled(ARM).
>
> For tested Trats2 device, this was done in three steps.
>
> First was enable the arch memcpy and memset.
> The second step was enable memset for .bss clear.
> The third step for reduce this operation is to keep .bss section
> small as possible.
>
> The .bss section will grow if we have a lot of static variables.
> This section is cleared before jump to the relocated U-Boot,
> and it's done word by word. To reduce the time for this step,
> we can enable arch memset, which uses multiple ARM registers.
>
> For configs with DFU enabled, we can find the dfu buffer in this section,
> which has at least 8MB (32MB for trats2). This is a lot of useless data,
> which is not required for standard boot. So this buffer should be dynamic
> allocated.
>
> Przemyslaw Marczak (3):
> exynos: config: enable arch memcpy and arch memset
> arm: relocation: clear .bss section with arch memset if defined
> dfu: mmc: file buffer: remove static allocation
>
> arch/arm/lib/crt0.S | 10 +++++++++-
> drivers/dfu/dfu_mmc.c | 25 ++++++++++++++++++++++---
> include/configs/exynos-common.h | 3 +++
> 3 files changed, 34 insertions(+), 4 deletions(-)

Looking at the commit messages of this patchset I can conclude that your
overall boot time reduction is:

from ~1527ms
to ~464ms

This is amazing! Congrats. :)

We really should in general make more use of the optimized functions and
take care that the buffers (e.g. the DFU buffer in this case) are used
in a sane way.

Thanks,
Stefan