AES-NI XTS To See 2~3x Performance Recovery After Regressing Hard From Retpolines
An Anonymous Coward writes:
https://www.phoronix.com/scan.php?page=news_item&px=AES-NI-XTS-Retpolines-Regress
It seems AES-NI XTS performance regressing hard from Retpolines went unnoticed when mitigating Spectre. This happened due to extensive use of indirect calls when processing small quantities of data. But thankfully Ard Biesheuvel investigated it and worked out a backport-friendly fix to address most of the regression. But then for future kernel releases is also a rewritten XTS implementation that is more flexible and avoids the nasty issues that led to the poor performance in the first place under Retpolines.
In the end the new patches allow improving the performance around ~2x for 1k/4k blocks and 3x for 1k blocks that require cipher text stealing.
[Ed Note - It's interesting that the performance hit from the Retpolines changes wasn't noticed before.]
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