Ubuntu
linux package

  1. Oracular (24.10)
  2. Bug #2071471
  3. Comment #2

Comment 2 for bug 2071471

Revision history for this message
Kleber Sacilotto de Souza (kleber-souza) wrote :

Upstream commit b2b97a62f055dd638f7f02087331a8380d8f139a changes the s390x defconfig's, which don't impact the Ubuntu kernel configs.

Looking at the configs for the 22.04 generic kernel, 'CONFIG_IOMMU_DEFAULT_DMA_STRICT=y' seems to be set for s390x on all Ubuntu 5.15 generic kernel builds as well. Therefore it doesn't seem the config has regressed, and although changing the kernel parameter during the boot time improves the performance it is likely not the only aspect causing the degradation.

Can IBM please confirm which 22.04 kernel version doesn't show the performance degradation and what are the config values for 'CONFIG_IOMMU_DEFAULT_DMA_STRICT' and 'CONFIG_IOMMU_DEFAULT_DMA_LAZY' on the running kernel?

Before changing the kernel config I would like to gather some more information to assess the consequences of the change and whether we need to make other changes as well.

Thank you.