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| author | Cassio Neri <[email protected]> | 2021-06-22 21:36:16 +0000 |
|---|---|---|
| committer | Thomas Gleixner <[email protected]> | 2021-06-24 09:51:59 +0000 |
| commit | 276010551664f73b6f1616dde471d6f0d63a73ba (patch) | |
| tree | 36bdb68afbbc7088b00c1ea0c9c55e8693b16960 /tools/perf/scripts/python/failed-syscalls-by-pid.py | |
| parent | clockevents: Use list_move() instead of list_del()/list_add() (diff) | |
| download | kernel-276010551664f73b6f1616dde471d6f0d63a73ba.tar.gz kernel-276010551664f73b6f1616dde471d6f0d63a73ba.zip | |
time: Improve performance of time64_to_tm()
The current implementation of time64_to_tm() contains unnecessary loops,
branches and look-up tables. The new one uses an arithmetic-based algorithm
appeared in [1] and is approximately 3x faster (YMMV).
The drawback is that the new code isn't intuitive and contains many 'magic
numbers' (not unusual for this type of algorithm). However, [1] justifies
all those numbers and, given this function's history, the code is unlikely
to need much maintenance, if any at all.
Add a KUnit test for it which checks every day in a 160,000 years interval
centered at 1970-01-01 against the expected result.
[1] Neri, Schneider, "Euclidean Affine Functions and Applications to
Calendar Algorithms". https://arxiv.org/abs/2102.06959
Signed-off-by: Cassio Neri <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Diffstat (limited to 'tools/perf/scripts/python/failed-syscalls-by-pid.py')
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