On Fri, Jul 28, 2023 at 05:51:46PM +0000, Long Li wrote: > > Subject: Re: [PATCH v4 1/1] RDMA/mana_ib: Add EQ interrupt support to mana ib > > driver. > > > > On Fri, Jul 28, 2023 at 05:07:49PM +0000, Wei Hu wrote: > > > Add EQ interrupt support for mana ib driver. Allocate EQs per ucontext > > > to receive interrupt. Attach EQ when CQ is created. Call CQ interrupt > > > handler when completion interrupt happens. EQs are destroyed when > > > ucontext is deallocated. > > > > It seems strange that interrupts would be somehow linked to a ucontext? > > interrupts are highly limited, you can DOS the entire system if someone abuses > > this. > > > > Generally I expect a properly functioning driver to use one interrupt per CPU core. > > Yes, MANA uses one interrupt per CPU. One interrupt is shared among multiple > EQs. So you have another multiplexing layer between the interrupt and the EQ? That is alot of multiplexing layers.. > > You should tie the CQ to a shared EQ belong to the core that the CQ wants to have > > affinity to. > > The reason for using a separate EQ for a ucontext, is for preventing DOS. If we use > a shared EQ, a single ucontext can storm this shared EQ affecting > other users. With a proper design it should not be possible. The CQ adds an entry to the EQ and that should be rate limited by the ability of userspace to schedule to re-arm the CQ. Jason
