** Also affects: linux (Ubuntu Xenial)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Xenial)
Importance: Undecided => High
** Changed in: linux (Ubuntu Xenial)
Status: New => Fix Committed
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https://bugs.launchpad.net/bugs/1606147
Title:
[APL][SAUCE] Slow system response time due to a monitor bug
Status in HWE Next:
Confirmed
Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Xenial:
Fix Committed
Bug description:
[Impact]
We've found a bug on some Apollo Lake system makes it runs very slow.
From upstream it is caused by following reason:
"Monitored cached line may not wake up from mwait on certain Goldmont
based CPUs. This patch will avoid calling
current_set_polling_and_test() and thereby not set the TIF_ flag. The
result is that we'll always send IPIs for wakeups."
[Fix]
Upstream already provided a workaround[1] to fix this problem. This
patches haven't been merged in latest(v4.7) release but already in
linux-next.
To fix this issue in Xenial it also needs another commit introduces
macros use in the workaround:
commit 970442c599b22ccd644ebfe94d1d303bf6f87c05
Author: Dave Hansen <d...@sr71.net>
Date: Thu Jun 2 17:19:27 2016 -0700
x86/cpu/intel: Introduce macros for Intel family numbers
This workaround checks CPU families and certain features, so no
further regressions is expected
[1]: https://lkml.org/lkml/2016/7/6/469
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