| Message ID | 20241027040700.1616307-1-csander@purestorage.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | mlx5: only schedule EQ comp tasklet if necessary | expand |
Hi > From: Caleb Sander Mateos <csander@purestorage.com> > Sent: Sunday, October 27, 2024 9:37 AM > > Currently, the mlx5_eq_comp_int() interrupt handler schedules a tasklet to call > mlx5_cq_tasklet_cb() if it processes any completions. For CQs whose > completions don't need to be processed in tasklet context, this overhead is > unnecessary. Atomic operations are needed to schedule, lock, and clear the > tasklet. And when mlx5_cq_tasklet_cb() runs, it acquires a spin lock to access > the list of CQs enqueued for processing. > > Schedule the tasklet in mlx5_add_cq_to_tasklet() instead to avoid this > overhead. mlx5_add_cq_to_tasklet() is responsible for enqueuing the CQs to > be processed in tasklet context, so it can schedule the tasklet. CQs that need > tasklet processing have their interrupt comp handler set to > mlx5_add_cq_to_tasklet(), so they will schedule the tasklet. CQs that don't > need tasklet processing won't schedule the tasklet. To avoid scheduling the > tasklet multiple times during the same interrupt, only schedule the tasklet in > mlx5_add_cq_to_tasklet() if the tasklet work queue was empty before the > new CQ was pushed to it. > > Note that the mlx4 driver works the same way: it schedules the tasklet in > mlx4_add_cq_to_tasklet() and only if the work queue was empty before. > > Signed-off-by: Caleb Sander Mateos <csander@purestorage.com> > --- > drivers/net/ethernet/mellanox/mlx5/core/cq.c | 5 +++++ > drivers/net/ethernet/mellanox/mlx5/core/eq.c | 5 +---- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > index 4caa1b6f40ba..25f3b26db729 100644 > --- a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > +++ b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > @@ -69,22 +69,27 @@ void mlx5_cq_tasklet_cb(struct tasklet_struct *t) > static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq, > struct mlx5_eqe *eqe) > { > unsigned long flags; > struct mlx5_eq_tasklet *tasklet_ctx = cq->tasklet_ctx.priv; > + bool schedule_tasklet = false; > > spin_lock_irqsave(&tasklet_ctx->lock, flags); > /* When migrating CQs between EQs will be implemented, please note > * that you need to sync this point. It is possible that > * while migrating a CQ, completions on the old EQs could > * still arrive. > */ > if (list_empty_careful(&cq->tasklet_ctx.list)) { > mlx5_cq_hold(cq); > + schedule_tasklet = list_empty(&tasklet_ctx->list); > list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list); > } > spin_unlock_irqrestore(&tasklet_ctx->lock, flags); > + > + if (schedule_tasklet) > + tasklet_schedule(&tasklet_ctx->task); > } > > /* Callers must verify outbox status in case of err */ int mlx5_create_cq(struct > mlx5_core_dev *dev, struct mlx5_core_cq *cq, > u32 *in, int inlen, u32 *out, int outlen) diff --git > a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > index 68cb86b37e56..66fc17d9c949 100644 > --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > @@ -112,17 +112,17 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > struct mlx5_eq_comp *eq_comp = > container_of(nb, struct mlx5_eq_comp, irq_nb); > struct mlx5_eq *eq = &eq_comp->core; > struct mlx5_eqe *eqe; > int num_eqes = 0; > - u32 cqn = -1; > > eqe = next_eqe_sw(eq); > if (!eqe) > goto out; > > do { > + u32 cqn; > struct mlx5_core_cq *cq; > A small nit, cqn should be declared after cq to follow the netdev coding guidelines of [1]. > /* Make sure we read EQ entry contents after we've > * checked the ownership bit. > */ > @@ -145,13 +145,10 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > } while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = > next_eqe_sw(eq))); > > out: > eq_update_ci(eq, 1); > > - if (cqn != -1) > - tasklet_schedule(&eq_comp->tasklet_ctx.task); > - Current code processes many EQEs and performs the check for tasklet_schedule only once in the cqn check. While this change, on every EQE, the additional check will be done. This will marginally make the interrupt handler slow. Returning a bool from comp() wont be good either, and we cannot inline things here due to function pointer. The cost of scheduling null tasklet is higher than this if (schedule_tasklet) check. In other series internally, I am working to reduce the cost of comp() itself unrelated to this change. so it ok to have the additional check introduced here. Apart from that, Reviewed-by: Parav Pandit <parav@nvidia.com> [1] https://elixir.bootlin.com/linux/v6.11.5/source/Documentation/process/maintainer-netdev.rst#L358 > return 0; > } > > /* Some architectures don't latch interrupts when they are disabled, so using > * mlx5_eq_poll_irq_disabled could end up losing interrupts while trying to > -- > 2.45.2 >
On Mon, Oct 28, 2024 at 9:08 PM Parav Pandit <parav@nvidia.com> wrote: > > Hi > > > From: Caleb Sander Mateos <csander@purestorage.com> > > Sent: Sunday, October 27, 2024 9:37 AM > > > > Currently, the mlx5_eq_comp_int() interrupt handler schedules a tasklet to call > > mlx5_cq_tasklet_cb() if it processes any completions. For CQs whose > > completions don't need to be processed in tasklet context, this overhead is > > unnecessary. Atomic operations are needed to schedule, lock, and clear the > > tasklet. And when mlx5_cq_tasklet_cb() runs, it acquires a spin lock to access > > the list of CQs enqueued for processing. > > > > Schedule the tasklet in mlx5_add_cq_to_tasklet() instead to avoid this > > overhead. mlx5_add_cq_to_tasklet() is responsible for enqueuing the CQs to > > be processed in tasklet context, so it can schedule the tasklet. CQs that need > > tasklet processing have their interrupt comp handler set to > > mlx5_add_cq_to_tasklet(), so they will schedule the tasklet. CQs that don't > > need tasklet processing won't schedule the tasklet. To avoid scheduling the > > tasklet multiple times during the same interrupt, only schedule the tasklet in > > mlx5_add_cq_to_tasklet() if the tasklet work queue was empty before the > > new CQ was pushed to it. > > > > Note that the mlx4 driver works the same way: it schedules the tasklet in > > mlx4_add_cq_to_tasklet() and only if the work queue was empty before. > > > > Signed-off-by: Caleb Sander Mateos <csander@purestorage.com> > > --- > > drivers/net/ethernet/mellanox/mlx5/core/cq.c | 5 +++++ > > drivers/net/ethernet/mellanox/mlx5/core/eq.c | 5 +---- > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > index 4caa1b6f40ba..25f3b26db729 100644 > > --- a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > @@ -69,22 +69,27 @@ void mlx5_cq_tasklet_cb(struct tasklet_struct *t) > > static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq, > > struct mlx5_eqe *eqe) > > { > > unsigned long flags; > > struct mlx5_eq_tasklet *tasklet_ctx = cq->tasklet_ctx.priv; > > + bool schedule_tasklet = false; > > > > spin_lock_irqsave(&tasklet_ctx->lock, flags); > > /* When migrating CQs between EQs will be implemented, please note > > * that you need to sync this point. It is possible that > > * while migrating a CQ, completions on the old EQs could > > * still arrive. > > */ > > if (list_empty_careful(&cq->tasklet_ctx.list)) { > > mlx5_cq_hold(cq); > > + schedule_tasklet = list_empty(&tasklet_ctx->list); > > list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list); > > } > > spin_unlock_irqrestore(&tasklet_ctx->lock, flags); > > + > > + if (schedule_tasklet) > > + tasklet_schedule(&tasklet_ctx->task); > > } > > > > /* Callers must verify outbox status in case of err */ int mlx5_create_cq(struct > > mlx5_core_dev *dev, struct mlx5_core_cq *cq, > > u32 *in, int inlen, u32 *out, int outlen) diff --git > > a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > index 68cb86b37e56..66fc17d9c949 100644 > > --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > @@ -112,17 +112,17 @@ static int mlx5_eq_comp_int(struct notifier_block > > *nb, > > struct mlx5_eq_comp *eq_comp = > > container_of(nb, struct mlx5_eq_comp, irq_nb); > > struct mlx5_eq *eq = &eq_comp->core; > > struct mlx5_eqe *eqe; > > int num_eqes = 0; > > - u32 cqn = -1; > > > > eqe = next_eqe_sw(eq); > > if (!eqe) > > goto out; > > > > do { > > + u32 cqn; > > struct mlx5_core_cq *cq; > > > A small nit, cqn should be declared after cq to follow the netdev coding guidelines of [1]. Sure, will fix. Thanks for the reference. > > > /* Make sure we read EQ entry contents after we've > > * checked the ownership bit. > > */ > > @@ -145,13 +145,10 @@ static int mlx5_eq_comp_int(struct notifier_block > > *nb, > > } while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = > > next_eqe_sw(eq))); > > > > out: > > eq_update_ci(eq, 1); > > > > - if (cqn != -1) > > - tasklet_schedule(&eq_comp->tasklet_ctx.task); > > - > Current code processes many EQEs and performs the check for tasklet_schedule only once in the cqn check. > While this change, on every EQE, the additional check will be done. > This will marginally make the interrupt handler slow. > Returning a bool from comp() wont be good either, and we cannot inline things here due to function pointer. > > The cost of scheduling null tasklet is higher than this if (schedule_tasklet) check. > In other series internally, I am working to reduce the cost of comp() itself unrelated to this change. > so it ok to have the additional check introduced here. Right, there's definitely a tradeoff here. From what I could tell, there is only one CQ type that processes completions in tasklet context (user Infiniband CQs, running mlx5_ib_cq_comp()). All others handle their completions in interrupt context. Ideally the CQ types that don't need it would not pay the cost of the tasklet schedule and execution. There are several atomic operations involved in the tasklet path which are fairly expensive. In our TCP-heavy workload, we see 4% of the CPU time spent on the tasklet_trylock() in tasklet_action_common.constprop.0, with a smaller amount spent on the atomic operations in tasklet_schedule(), tasklet_clear_sched(), and acquiring the spinlock in mlx5_cq_tasklet_cb(). I agree the additional branch per EQE should be cheaper than scheduling the unused tasklet, but the cost would be paid by Infiniband workloads while non-Infiniband workloads see the benefit. How about instead scheduling the tasklet in mlx5_eq_comp_int() if any of the CQs have a tasklet completion handler? That should get the best of both worlds: skipping the tasklet schedule for CQs that don't need it while ensuring the tasklet is only scheduled once per interrupt. Something like this: diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c index 68cb86b37e56..f0ba3725b8e9 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c @@ -112,9 +112,9 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, struct mlx5_eq_comp *eq_comp = container_of(nb, struct mlx5_eq_comp, irq_nb); struct mlx5_eq *eq = &eq_comp->core; + bool schedule_tasklet = false; struct mlx5_eqe *eqe; int num_eqes = 0; - u32 cqn = -1; eqe = next_eqe_sw(eq); if (!eqe) @@ -122,6 +122,7 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, do { struct mlx5_core_cq *cq; + u32 cqn; /* Make sure we read EQ entry contents after we've * checked the ownership bit. @@ -134,6 +135,7 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, if (likely(cq)) { ++cq->arm_sn; cq->comp(cq, eqe); + schedule_tasklet |= !!cq->tasklet_ctx.comp; mlx5_cq_put(cq); } else { dev_dbg_ratelimited(eq->dev->device, @@ -147,7 +149,7 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, out: eq_update_ci(eq, 1); - if (cqn != -1) + if (schedule_tasklet) tasklet_schedule(&eq_comp->tasklet_ctx.task); return 0; Thanks, Caleb
> From: Caleb Sander <csander@purestorage.com> > Sent: Tuesday, October 29, 2024 10:02 PM > > On Mon, Oct 28, 2024 at 9:08 PM Parav Pandit <parav@nvidia.com> wrote: > > > > Hi > > > > > From: Caleb Sander Mateos <csander@purestorage.com> > > > Sent: Sunday, October 27, 2024 9:37 AM > > > > > > Currently, the mlx5_eq_comp_int() interrupt handler schedules a > > > tasklet to call > > > mlx5_cq_tasklet_cb() if it processes any completions. For CQs whose > > > completions don't need to be processed in tasklet context, this > > > overhead is unnecessary. Atomic operations are needed to schedule, > > > lock, and clear the tasklet. And when mlx5_cq_tasklet_cb() runs, it > > > acquires a spin lock to access the list of CQs enqueued for processing. > > > > > > Schedule the tasklet in mlx5_add_cq_to_tasklet() instead to avoid > > > this overhead. mlx5_add_cq_to_tasklet() is responsible for enqueuing > > > the CQs to be processed in tasklet context, so it can schedule the > > > tasklet. CQs that need tasklet processing have their interrupt comp > > > handler set to mlx5_add_cq_to_tasklet(), so they will schedule the > > > tasklet. CQs that don't need tasklet processing won't schedule the > > > tasklet. To avoid scheduling the tasklet multiple times during the > > > same interrupt, only schedule the tasklet in > > > mlx5_add_cq_to_tasklet() if the tasklet work queue was empty before > > > the new CQ was pushed to it. > > > > > > Note that the mlx4 driver works the same way: it schedules the > > > tasklet in > > > mlx4_add_cq_to_tasklet() and only if the work queue was empty before. > > > > > > Signed-off-by: Caleb Sander Mateos <csander@purestorage.com> > > > --- > > > drivers/net/ethernet/mellanox/mlx5/core/cq.c | 5 +++++ > > > drivers/net/ethernet/mellanox/mlx5/core/eq.c | 5 +---- > > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > > b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > > index 4caa1b6f40ba..25f3b26db729 100644 > > > --- a/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/cq.c > > > @@ -69,22 +69,27 @@ void mlx5_cq_tasklet_cb(struct tasklet_struct > > > *t) static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq, > > > struct mlx5_eqe *eqe) { > > > unsigned long flags; > > > struct mlx5_eq_tasklet *tasklet_ctx = cq->tasklet_ctx.priv; > > > + bool schedule_tasklet = false; > > > > > > spin_lock_irqsave(&tasklet_ctx->lock, flags); > > > /* When migrating CQs between EQs will be implemented, please > note > > > * that you need to sync this point. It is possible that > > > * while migrating a CQ, completions on the old EQs could > > > * still arrive. > > > */ > > > if (list_empty_careful(&cq->tasklet_ctx.list)) { > > > mlx5_cq_hold(cq); > > > + schedule_tasklet = list_empty(&tasklet_ctx->list); > > > list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list); > > > } > > > spin_unlock_irqrestore(&tasklet_ctx->lock, flags); > > > + > > > + if (schedule_tasklet) > > > + tasklet_schedule(&tasklet_ctx->task); > > > } > > > > > > /* Callers must verify outbox status in case of err */ int > > > mlx5_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq, > > > u32 *in, int inlen, u32 *out, int outlen) diff > > > --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > > b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > > index 68cb86b37e56..66fc17d9c949 100644 > > > --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > > > @@ -112,17 +112,17 @@ static int mlx5_eq_comp_int(struct > > > notifier_block *nb, > > > struct mlx5_eq_comp *eq_comp = > > > container_of(nb, struct mlx5_eq_comp, irq_nb); > > > struct mlx5_eq *eq = &eq_comp->core; > > > struct mlx5_eqe *eqe; > > > int num_eqes = 0; > > > - u32 cqn = -1; > > > > > > eqe = next_eqe_sw(eq); > > > if (!eqe) > > > goto out; > > > > > > do { > > > + u32 cqn; > > > struct mlx5_core_cq *cq; > > > > > A small nit, cqn should be declared after cq to follow the netdev coding > guidelines of [1]. > > Sure, will fix. Thanks for the reference. > > > > > > /* Make sure we read EQ entry contents after we've > > > * checked the ownership bit. > > > */ > > > @@ -145,13 +145,10 @@ static int mlx5_eq_comp_int(struct > > > notifier_block *nb, > > > } while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = > > > next_eqe_sw(eq))); > > > > > > out: > > > eq_update_ci(eq, 1); > > > > > > - if (cqn != -1) > > > - tasklet_schedule(&eq_comp->tasklet_ctx.task); > > > - > > Current code processes many EQEs and performs the check for > tasklet_schedule only once in the cqn check. > > While this change, on every EQE, the additional check will be done. > > This will marginally make the interrupt handler slow. > > Returning a bool from comp() wont be good either, and we cannot inline > things here due to function pointer. > > > > The cost of scheduling null tasklet is higher than this if (schedule_tasklet) > check. > > In other series internally, I am working to reduce the cost of comp() itself > unrelated to this change. > > so it ok to have the additional check introduced here. > > Right, there's definitely a tradeoff here. > From what I could tell, there is only one CQ type that processes completions > in tasklet context (user Infiniband CQs, running mlx5_ib_cq_comp()). All > others handle their completions in interrupt context. Ideally the CQ types > that don't need it would not pay the cost of the tasklet schedule and > execution. There are several atomic operations involved in the tasklet path > which are fairly expensive. In our TCP-heavy workload, we see 4% of the CPU > time spent on the > tasklet_trylock() in tasklet_action_common.constprop.0, with a smaller > amount spent on the atomic operations in tasklet_schedule(), > tasklet_clear_sched(), and acquiring the spinlock in mlx5_cq_tasklet_cb(). Please include this perf stats in the commit log in v1, which helps to decide on the trade-off and also quantifies it. > I agree the additional branch per EQE should be cheaper than scheduling the > unused tasklet, but the cost would be paid by Infiniband workloads while > non-Infiniband workloads see the benefit. > How about instead scheduling the tasklet in mlx5_eq_comp_int() if any of > the CQs have a tasklet completion handler? That should get the best of both > worlds: skipping the tasklet schedule for CQs that don't need it while > ensuring the tasklet is only scheduled once per interrupt. > Something like this: > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > index 68cb86b37e56..f0ba3725b8e9 100644 > --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c > +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c > @@ -112,9 +112,9 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > struct mlx5_eq_comp *eq_comp = > container_of(nb, struct mlx5_eq_comp, irq_nb); > struct mlx5_eq *eq = &eq_comp->core; > + bool schedule_tasklet = false; > struct mlx5_eqe *eqe; > int num_eqes = 0; > - u32 cqn = -1; > > eqe = next_eqe_sw(eq); > if (!eqe) > @@ -122,6 +122,7 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > > do { > struct mlx5_core_cq *cq; > + u32 cqn; > > /* Make sure we read EQ entry contents after we've > * checked the ownership bit. > @@ -134,6 +135,7 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > if (likely(cq)) { > ++cq->arm_sn; > cq->comp(cq, eqe); > + schedule_tasklet |= !!cq->tasklet_ctx.comp; > mlx5_cq_put(cq); > } else { > dev_dbg_ratelimited(eq->dev->device, > @@ -147,7 +149,7 @@ static int mlx5_eq_comp_int(struct notifier_block > *nb, > out: > eq_update_ci(eq, 1); > > - if (cqn != -1) > + if (schedule_tasklet) > tasklet_schedule(&eq_comp->tasklet_ctx.task); > > return 0; > The issue in the above change is, it makes assumption of CQ layer (upper layer above interrupt) if tasklet to be used or not. I would rather keep the two layers separate as your patch. > Thanks, > Caleb
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cq.c b/drivers/net/ethernet/mellanox/mlx5/core/cq.c index 4caa1b6f40ba..25f3b26db729 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/cq.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/cq.c @@ -69,22 +69,27 @@ void mlx5_cq_tasklet_cb(struct tasklet_struct *t) static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq, struct mlx5_eqe *eqe) { unsigned long flags; struct mlx5_eq_tasklet *tasklet_ctx = cq->tasklet_ctx.priv; + bool schedule_tasklet = false; spin_lock_irqsave(&tasklet_ctx->lock, flags); /* When migrating CQs between EQs will be implemented, please note * that you need to sync this point. It is possible that * while migrating a CQ, completions on the old EQs could * still arrive. */ if (list_empty_careful(&cq->tasklet_ctx.list)) { mlx5_cq_hold(cq); + schedule_tasklet = list_empty(&tasklet_ctx->list); list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list); } spin_unlock_irqrestore(&tasklet_ctx->lock, flags); + + if (schedule_tasklet) + tasklet_schedule(&tasklet_ctx->task); } /* Callers must verify outbox status in case of err */ int mlx5_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq, u32 *in, int inlen, u32 *out, int outlen) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c index 68cb86b37e56..66fc17d9c949 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c @@ -112,17 +112,17 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, struct mlx5_eq_comp *eq_comp = container_of(nb, struct mlx5_eq_comp, irq_nb); struct mlx5_eq *eq = &eq_comp->core; struct mlx5_eqe *eqe; int num_eqes = 0; - u32 cqn = -1; eqe = next_eqe_sw(eq); if (!eqe) goto out; do { + u32 cqn; struct mlx5_core_cq *cq; /* Make sure we read EQ entry contents after we've * checked the ownership bit. */ @@ -145,13 +145,10 @@ static int mlx5_eq_comp_int(struct notifier_block *nb, } while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = next_eqe_sw(eq))); out: eq_update_ci(eq, 1); - if (cqn != -1) - tasklet_schedule(&eq_comp->tasklet_ctx.task); - return 0; } /* Some architectures don't latch interrupts when they are disabled, so using * mlx5_eq_poll_irq_disabled could end up losing interrupts while trying to
Currently, the mlx5_eq_comp_int() interrupt handler schedules a tasklet to call mlx5_cq_tasklet_cb() if it processes any completions. For CQs whose completions don't need to be processed in tasklet context, this overhead is unnecessary. Atomic operations are needed to schedule, lock, and clear the tasklet. And when mlx5_cq_tasklet_cb() runs, it acquires a spin lock to access the list of CQs enqueued for processing. Schedule the tasklet in mlx5_add_cq_to_tasklet() instead to avoid this overhead. mlx5_add_cq_to_tasklet() is responsible for enqueuing the CQs to be processed in tasklet context, so it can schedule the tasklet. CQs that need tasklet processing have their interrupt comp handler set to mlx5_add_cq_to_tasklet(), so they will schedule the tasklet. CQs that don't need tasklet processing won't schedule the tasklet. To avoid scheduling the tasklet multiple times during the same interrupt, only schedule the tasklet in mlx5_add_cq_to_tasklet() if the tasklet work queue was empty before the new CQ was pushed to it. Note that the mlx4 driver works the same way: it schedules the tasklet in mlx4_add_cq_to_tasklet() and only if the work queue was empty before. Signed-off-by: Caleb Sander Mateos <csander@purestorage.com> --- drivers/net/ethernet/mellanox/mlx5/core/cq.c | 5 +++++ drivers/net/ethernet/mellanox/mlx5/core/eq.c | 5 +---- 2 files changed, 6 insertions(+), 4 deletions(-)