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------- Comment From brueckner@xxxxxxxxxx 2016-03-08 03:20 EDT-------
(In reply to comment #4)
>
> The requests below two keys are currently out of scope, with the generic
> kernel config policy for Ubuntu:
> CONFIG_PREEMPT_NONE

And for disabling preemption:

We only have performance numbers for non-preemptible kernels. While kernel
preemption generally should work from a functional point of view on s390,
we do not have numbers about the performance costs. Nor do we have any
production systems running with kernel preemption enabled currently.
Therefore let's please switch to PREEMPT_NONE which has proven to work.

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https://bugs.launchpad.net/bugs/1543165

Title:
  kernel: update kernel configuration

Status in linux package in Ubuntu:
  Triaged

Bug description:
  == Comment: #0 - Hendrik Brueckner <brueckner@xxxxxxxxxx> - 2016-02-08 09:41:49 ==
  The below mentioned kernel configuration options are still not yet integrated into the Ubuntu kernel. In addition to the discussions on the skipper mailing list, hereby the bugzilla / launchpad to integrate and update the kernel configuration.

  > Short explaination for all requested changes:
  >
  > CONFIG_NUMA (and all related config options):
  > s390 gained fake NUMA support with kernel version 4.3. Performance
  > measurements did show that this helps for very large machines (lot's of
  > memory), and also doesn't hurt for small machines.  Therfore the config
  > option should be enabled.
  >
  > CONFIG_PREEMPT_NONE:
  > We only have performance numbers for non-preemptible kernels. While kernel
  > preemption generally should work from a functional point of view on s390,
  > we do not have numbers about the performance costs. Nor do we have any
  > production systems running with kernel preemption enabled currently.
  > Therefore let's please switch to PREEMPT_NONE which has proven to work.
  >
  > CONFIG_SCSI_SCAN_ASYNC:
  > Hendrik already requested to disable this config option.
  >
  > CONFIG_REGMAP,
  > CONFIG_NET_VENDOR_EMULEX,
  > CONFIG_BE2NET,
  > CONFIG_BE2NET_VXLAN,
  > CONFIG_NET_VENDOR_SYNOPSYS,
  > CONFIG_NVMEM:
  > Looks like all of these crept in with the kernel update to 4.3. None of
  > these are relevant to s390 and can be disabled.

  An updated config patch to the kernel version above will be added

  
  ====
  Kernel-Description: s390x -- clear out hardware related configuration item

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