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

[Przemyslaw Marczak]

Hello,

On 01/28/2015 03:18 PM, Pantelis Antoniou wrote:
> Hi Przemyslaw,
>
>> On Jan 28, 2015, at 16:10 , Przemyslaw Marczak <p.marczak at samsung.com> wrote:
>>
>> Hello Stefan,
>>
>> On 01/28/2015 02:12 PM, Stefan Roese wrote:
>>> 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. :)
>>>
>>
>> Thank you. I was also amazed.
>>
>> The time results are taken with from the clock cycle counter, I think it's reliable. Some day I would like to check it using the oscilloscope.
>>
>>> 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
>>>
>>>
>>
>> Yes you're right, I thought that Exynos config has enabled arch memcpy/set lib, before I checked this…
>>
>
> Those numbers are indeed incredible; I suppose the caches are disabled?
>
>

The caches are enabled after the relocation, in one of board_init_r calls.

>> Best regards,
>> --
>> Przemyslaw Marczak
>> Samsung R&D Institute Poland
>> Samsung Electronics
>> p.marczak at samsung.com
>
> Regards
>
> — Pantelis
>
>

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com