arm: reduce .bss section clear time
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Cover letter [U-Boot] [PATCH 0/3] arm: reduce .bss section clear time
Hello,
Quoted 62 lines · Pantelis Antoniou
Hi Przemyslaw,
Quoted 60 lines · Przemyslaw Marczak
Hello Stefan,
Quoted 33 lines · Stefan Roese
Hi Przemyslaw,
Quoted 25 lines · Przemyslaw Marczak
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 allocationQuoted 4 lines
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(-)Quoted 8 lines
Looking at the commit messages of this patchset I can conclude that your overall boot time reduction is:
from ~1527ms
to ~464msThis 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.
Quoted 8 lines
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
Quoted 6 lines
Quoted 2 lines
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.
Quoted 7 lines
Quoted 6 lines
Best regards,
--
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com
Quoted 5 lines
Regards
? Pantelis
Best regards,
Signature · 4 lines
Przemyslaw Marczak Samsung R&D Institute Poland Samsung Electronics p.marczak at samsung.com