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There exists a bug in which a 'perfect storm' can occur and cause interrupts to fail to be correctly affinitized. This causes unexpected behavior and has a substantial impact on performance when it happens. The bug occurs if there is heavy traffic, any number of CPUs that have an i40e interrupt are pegged at 100%, and the interrupt afffinity for those CPUs is changed. Instead of moving to the new CPU, the interrupt continues to be polled while there is heavy traffic. The bug is most readily realized as the driver is first brought up and all interrupts start on CPU0. If there is heavy traffic and the interrupt starts polling before the interrupt is affinitized, the interrupt will be stuck on CPU0 until traffic stops. The bug, however, can also be wrought out more simply by affinitizing all the interrupts to a single CPU and then attempting to move any of those interrupts off while there is heavy traffic. This patch fixes the bug by registering for update notifications from the kernel when the interrupt affinity changes. When that fires, we cache the intended affinity mask. Then, while polling, if the cpu is pegged at 100% and we failed to clean the rings, we check to make sure we have the correct affinity and stop polling if we're firing on the wrong CPU. When the kernel successfully moves the interrupt, it will start polling on the correct CPU. The performance impact is minimal since the only time this section gets executed is when performance is already compromised by the CPU. Change-ID: I4410a880159b9dba1f8297aa72bef36dca34e830 Signed-off-by: Alan Brady <alan.brady@intel.com> Tested-by: Andrew Bowers <andrewx.bowers@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> |
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| e1000 | ||
| e1000e | ||
| fm10k | ||
| i40e | ||
| i40evf | ||
| igb | ||
| igbvf | ||
| ixgb | ||
| ixgbe | ||
| ixgbevf | ||
| e100.c | ||
| Kconfig | ||
| Makefile | ||