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[v2,0/3] part_efi: cache last scanned GPT for next partition

Message ID 20250408-topic-gpt-cache-v2-0-de76e47debb7@linaro.org
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Series part_efi: cache last scanned GPT for next partition | expand

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Neil Armstrong April 8, 2025, 9:13 a.m. UTC 
The actual architecture of the EFI part parser means the
entire GPT partition table needs to be parsed for each
part_info() callback.

Since the default part scan code will always scan up to
128 partitions for a block, and devices with an UFS chip
with up to 8 LUNs are very common in the field, this means
a complete GPT parsing and validation will be done
up to 1024 times instead of 8 on such devices.

The GPT parsing can be cached between each part_info()
call speed up to 3x on the worse condition when the CPU
i-cache and d-cache are disabled, like in the SPL.

The new part API implementation does caching each time
a correct GPT has been parsed and verified and will match
the blk_desc and LBA to serve the cached data or force
a re-parsing.

In order to allow GPT manipulation, the new API is only
called when scanning the partitions for a disk, all the
calls will be called uncached.

On the SM8650 QRD platform with a KIOXIA THGJFJT1E45BATPC
configured with 8 LUNs, the scsi scan takes 0.2s with both
CPU caches enabled, but when disabling both CPU caches it
goes up to 4s to do the full scan of all 8 LUN partitions.

With this change the scan takes only 0.18s with both CPU
caches enabled running 1.1x times faster, and with both CPU
caches disabled the full scan takes only 1.27s running
3x faster.

While 20ms could look negligeable, it's still a 20ms gain
in the boot flow and a non negligeable reduction in
calculation and memory allocation since for each scan
it would allocate and free the gpt_pte table up to
1024 times, now it would only do 8 allocations, reducing
memory fragmentation.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
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Changes in v2:
- add part_info_get_cached API
- only use cache when called from part_info_get_cached
- Link to v1: https://lore.kernel.org/all/20250327-u-boot-efi-part-cache-v1-1-be6b69c0698b@linaro.org

---
Neil Armstrong (3):
      part: add part_get_info_cached() API
      part: efi: add GPT PTE cache used with part_get_info_cached() API
      block: use part_get_info_cached() API when scanning partitions

 disk/part.c                |  55 +++++++++++++++++-----
 disk/part_efi.c            | 114 ++++++++++++++++++++++++++++++++++++++-------
 drivers/block/blk-uclass.c |   7 ++-
 include/part.h             |  44 +++++++++++++++++
 4 files changed, 189 insertions(+), 31 deletions(-)
---
base-commit: 5ca70325b64f760bf4190f206a0e88dda495e3d2
change-id: 20250408-topic-gpt-cache-11f770f42f1e

Best regards,