lfs_bd_cmp() compares more bytes at one time #395
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It's very slowly to compare one byte at one time. Here are the performance I get from 128M spinand with NFTL by sequential writing. | file size | buffer size | write speed | | 10 MB | 0 B | 3206.01 KB/s | | 10 MB | 1 B | 2434.04 KB/s | | 10 MB | 2 B | 2685.78 KB/s | | 10 MB | 4 B | 2857.94 KB/s | | 10 MB | 8 B | 3060.68 KB/s | | 10 MB | 16 B | 3155.30 KB/s | | 10 MB | 64 B | 3193.68 KB/s | | 10 MB | 128 B | 3230.62 KB/s | | 10 MB | 256 B | 3153.03 KB/s | | 70 MB | 0 B | 2258.87 KB/s | | 70 MB | 1 B | 1827.83 KB/s | | 70 MB | 2 B | 1962.29 KB/s | | 70 MB | 4 B | 2074.01 KB/s | | 70 MB | 8 B | 2147.03 KB/s | | 70 MB | 64 B | 2179.92 KB/s | | 70 MB | 256 B | 2179.96 KB/s | The 0 Byte size means no validation and the 1 Byte size is how littlefs do before. Based on the above table and to save memory, comparing 8 bytes at one time is more wonderful. Signed-off-by: WeiXiong Liao <[email protected]>
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This looks reasonable to me.... |
thrasher8390
approved these changes
Mar 24, 2020
| uint8_t dat; | ||
| int err = lfs_bd_read(lfs, | ||
| for (lfs_off_t i = 0; i < size; i += diff) { | ||
| uint8_t dat[8]; |
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Why was 8 chosen.
Remember that this is being stored on the stack.
Any thoughts on making this configurable or reasons why it shouldn't be configurable?
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Too many configurations can be confusing.
I think 8 bytes is the best balance between performance and used space.
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Hi @gmpy, this is a great patch and great analysis! Sorry this PR has been hanging for so long. I wasn't able to make a release for a while, but will bring this in the next minor release. |
geky
approved these changes
Nov 16, 2020
This was referenced Dec 4, 2020
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It's very slowly to compare one byte at one time. Here are the
performance I get from 128M spinand with NFTL by sequential writing.
| file size | buffer size | write speed |
| 10 MB | 0 B | 3206.01 KB/s |
| 10 MB | 1 B | 2434.04 KB/s |
| 10 MB | 2 B | 2685.78 KB/s |
| 10 MB | 4 B | 2857.94 KB/s |
| 10 MB | 8 B | 3060.68 KB/s |
| 10 MB | 16 B | 3155.30 KB/s |
| 10 MB | 64 B | 3193.68 KB/s |
| 10 MB | 128 B | 3230.62 KB/s |
| 10 MB | 256 B | 3153.03 KB/s |
| 70 MB | 0 B | 2258.87 KB/s |
| 70 MB | 1 B | 1827.83 KB/s |
| 70 MB | 2 B | 1962.29 KB/s |
| 70 MB | 4 B | 2074.01 KB/s |
| 70 MB | 8 B | 2147.03 KB/s |
| 70 MB | 64 B | 2179.92 KB/s |
| 70 MB | 256 B | 2179.96 KB/s |
The 0 Byte size means no validation and the 1 Byte size is how
littlefs do before. Based on the above table and to save memory,
comparing 8 bytes at one time is more wonderful.
Signed-off-by: WeiXiong Liao [email protected]