Hi Mark:
I have some question related to gicv3 driver on 1 of N distribution
model.
Looking at the linux kernel implementation the interrupt is always
affined to the first online cpu and does not use the 1 of N distribution
model.
As per the Gic spec 1 of N model could help to achieve low latency as
handling the interrupts as there are more PE's participating in handling
the interrupt.
Is there a reason the Linux kernel driver does not implement the 1 of N
model?
Thanks,
Channa
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
On Tue, Nov 28, 2017 at 04:42:47PM -0800, ckadabi at codeaurora.org wrote:
Hi Mark:
Hi,
I'm afraid I don't know much about GICv3 or the irq infrastrcuture in
the kernel . Did you mean to ask Marc Zyngier (Cc'd)?
Thanks,
Mark.
I have some question related to gicv3 driver on 1 of N distribution model.
Looking at the linux kernel implementation the interrupt is always affined
to the first online cpu and does not use the 1 of N distribution model.
As per the Gic spec 1 of N model could help to achieve low latency as
handling the interrupts as there are more PE's participating in handling the
interrupt.
Is there a reason the Linux kernel driver does not implement the 1 of N
model?
Thanks,
Channa
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
Thanks Mark,
On 29/11/17 10:34, Mark Rutland wrote:
On Tue, Nov 28, 2017 at 04:42:47PM -0800, ckadabi at codeaurora.org wrote:
quoted
Hi Mark:
Hi,
I'm afraid I don't know much about GICv3 or the irq infrastrcuture in
the kernel . Did you mean to ask Marc Zyngier (Cc'd)?
Thanks,
Mark.
quoted
I have some question related to gicv3 driver on 1 of N distribution model.
Looking at the linux kernel implementation the interrupt is always affined
to the first online cpu and does not use the 1 of N distribution model.
As per the Gic spec 1 of N model could help to achieve low latency as
handling the interrupts as there are more PE's participating in handling the
interrupt.
Is there a reason the Linux kernel driver does not implement the 1 of N
model?
The 1-N model comes at the expense of interrupting all the participating
CPUs until one of them actually ACKs the interrupt (and the others only
see a spurious interrupt). This indeed reduces the latency to service
the interrupt, and kills the performance of all the CPUs. Not the
brightest thing, IMO.
It feels to me that a better option is to let an external agent spread
the interrupts on the less busy CPUs. Something like irqbalance...
Thanks,
M.
--
Jazz is not dead. It just smells funny...