[0/2] vTSC performance improvements

Message

Igor Druzhinin Dec. 13, 2019, 10:48 p.m. UTC

In our PV shim testing we've noticed constant lockups of guests with high
number of vCPUs assigned that usually happening when there is another guest
running on the same host. Reproing the problem manually and dumping shim
state immediately showed that most of the vCPUs are locked on vtsc_lock.
As PV shim guest always gets emulated TSC due to L1 Xen itself not being
provided with ITSC the ideal solution would be to try dropping the lock
entirely.

Igor Druzhinin (2):
  x86/time: drop vtsc_{kern,user}count debug counters
  x86/time: update vtsc_last with cmpxchg and drop vtsc_lock

 xen/arch/x86/domain.c        |  1 -
 xen/arch/x86/hvm/hvm.c       | 32 ++------------------------------
 xen/arch/x86/time.c          | 28 ++++++----------------------
 xen/include/asm-x86/domain.h |  5 -----
 4 files changed, 8 insertions(+), 58 deletions(-)