v1->v2: - Take out the queued unfair lock patches - Add a patch to simplify the PV unlock code - Move pending bit and statistics collection patches to the front - Keep vCPU kicking in pv_kick_node(), but defer it to unlock time when appropriate. - Change the wait-early patch to use adaptive spinning to better balance the difference effect on normal and over-committed guests. - Add patch-to-patch performance changes in the patch commit logs.
This patchset tries to improve the performance of both normal and over-commmitted VM guests. The kick-ahead and adaptive spinning patches are inspired by the "Do Virtual Machines Really Scale?" blog from Sanidhya Kashyap. Patch 1 simplifies the unlock code by doing unconditional vCPU kick when _Q_SLOW_VAL is set as the chance of spurious wakeup showing up in the statistical data that I collected was very low (1 or 2 occasionally). Patch 2 adds pending bit support to pvqspinlock improving performance at light load. Patch 3 allows the collection of various count data that are useful to see what is happening in the system. They do add a bit of overhead when enabled. This will slow the system a little bit. Patch 4 enables multiple vCPU kicks at unlock time, outside of the critical section. Coupled with patch 5 which defers kicking to unlock time, this will improve system performance in overcommitted guests and sometime even in normal guests. Patch 6 enables adaptive spinning in the queue nodes. This patch can lead to pretty big performance increase in over-committed guest at the expense of a slight performance hit in normal guests. Waiman Long (6): locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL locking/pvqspinlock: Add pending bit support locking/pvqspinlock: Collect slowpath lock statistics locking/pvqspinlock: Allow vCPUs kick-ahead locking/pvqspinlock: Opportunistically defer kicking to unlock time locking/pvqspinlock: Queue node adaptive spinning arch/x86/Kconfig | 7 + kernel/locking/qspinlock.c | 38 +++- kernel/locking/qspinlock_paravirt.h | 452 +++++++++++++++++++++++++++++++++-- 3 files changed, 473 insertions(+), 24 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
