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Cortex-A9 ARM Errata 845369

Question asked by Marc-Oliver Westerburg on Aug 26, 2015
Latest reply on Apr 12, 2016 by Nori Shinozaki

Apparently on 1st of April 2015 a work-around for ARM Cortex-A9 Errata #845369 has been added to public U-Boot repositories and this patch also is included in Freescale's most recent i.MX6x Android Release L5.0.0_1.0.0-ga, but nowhere else, so far (esp. not yet in the i.MX6x Yocto releases from Freescale).

 

The ARM Errata mentions "Setting this bit could possibly result in a visible drop in performance for routines that perform intensive memory

accesses, such as memset() or memcpy(). However, the workaround is not expected to create any significant performance degradation in most standard applications."

 

Brief tests on our i.MX6x-devices show that there is indeed a "visible drop in performance" for memset() and memcpy():

  • memset() performance drops down to <25% of its previous performance (yes, "down to" not "by")
  • memcpy() performance dropds down to ~50% of its previous performance

 

Has anybody made any more "real-world" experience with the performance-impact of the work-around for this errata #845369, so far (e.g. impact on graphics or video-performance, network performance, storage-media, etc)?

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