On Wed, Feb 15, 2017 at 4:04 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Wed, 2017-02-15 at 05:29 -0800, Eric Dumazet wrote: > >> >> mlx4_eq_int() is a hard irq handler. >> >> How a tasklet could run in the middle of it ? >> >> A tasklet is a softirq handler. > > Speaking of mlx4_eq_int() , 50% of cycles are spent on mb() (mfence) > in eq_set_ci() >
I wonder why you have so many interrupts ? don't you have some kind of interrupt moderation ? what test are you running that got your CPU so busy. > I wonder why this very expensive mb() is required, right before exiting > the interrupt handler. to make sure the HW knows we handled Completions up to (ci) consumer index. so it will generate next irq.
