> -----Original Message-----
> From: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Sent: Friday, October 11, 2019 12:39 PM
> To: Parav Pandit <parav@xxxxxxxxxxxx>
> Cc: linux-rdma@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v3] IB/core: Trace points for diagnosing completion queue
> issues
>
>
>
> > On Oct 11, 2019, at 1:26 PM, Parav Pandit <parav@xxxxxxxxxxxx> wrote:
> >
> >
> >
> >> -----Original Message-----
> >> From: linux-rdma-owner@xxxxxxxxxxxxxxx <linux-rdma-
> >> owner@xxxxxxxxxxxxxxx> On Behalf Of Chuck Lever
> >> Sent: Wednesday, October 9, 2019 11:55 AM
> >> To: linux-rdma@xxxxxxxxxxxxxxx
> >> Subject: [PATCH v3] IB/core: Trace points for diagnosing completion
> >> queue issues
> >>
> >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >> ---
> >> drivers/infiniband/core/Makefile | 2
> >> drivers/infiniband/core/cq.c | 29 +++--
> >> drivers/infiniband/core/trace.c | 14 ++
> >> include/rdma/ib_verbs.h | 2
> >> include/trace/events/rdma_core.h | 218
> >> ++++++++++++++++++++++++++++++++++++++
> >> 5 files changed, 255 insertions(+), 10 deletions(-) create mode
> >> 100644 drivers/infiniband/core/trace.c create mode 100644
> >> include/trace/events/rdma_core.h
> >>
> >> Changes since v2:
> >> - Removed extraneous changes to include/trace/events/rdma.h
> >>
> >> Changes since RFC:
> >> - Addressed comments from Parav Pandit <parav@xxxxxxxxxxxx>
> >>
> >>
> >> diff --git a/drivers/infiniband/core/Makefile
> >> b/drivers/infiniband/core/Makefile
> >> index 09881bd..68d9e27 100644
> >> --- a/drivers/infiniband/core/Makefile
> >> +++ b/drivers/infiniband/core/Makefile
> >> @@ -11,7 +11,7 @@ ib_core-y := packer.o ud_header.o
> >> verbs.o cq.o rw.o sysfs.o \
> >> device.o fmr_pool.o cache.o netlink.o \
> >> roce_gid_mgmt.o mr_pool.o addr.o
> >> sa_query.o \
> >> multicast.o mad.o smi.o agent.o mad_rmpp.o \
> >> - nldev.o restrack.o counters.o
> >> + nldev.o restrack.o counters.o trace.o
> >>
> >> ib_core-$(CONFIG_SECURITY_INFINIBAND) += security.o
> >> ib_core-$(CONFIG_CGROUP_RDMA) += cgroup.o diff --git
> >> a/drivers/infiniband/core/cq.c b/drivers/infiniband/core/cq.c index
> >> bbfded6..bcde992 100644
> >> --- a/drivers/infiniband/core/cq.c
> >> +++ b/drivers/infiniband/core/cq.c
> >> @@ -7,6 +7,8 @@
> >> #include <linux/slab.h>
> >> #include <rdma/ib_verbs.h>
> >>
> >> +#include <trace/events/rdma_core.h>
> >> +
> >> /* # of WCs to poll for with a single call to ib_poll_cq */
> >> #define IB_POLL_BATCH 16
> >> #define IB_POLL_BATCH_DIRECT 8
> >> @@ -41,6 +43,7 @@ static void ib_cq_rdma_dim_work(struct work_struct
> >> *w)
> >>
> >> dim->state = DIM_START_MEASURE;
> >>
> >> + trace_cq_modify(cq, comps, usec);
> >> cq->device->ops.modify_cq(cq, comps, usec); }
> >>
> >> @@ -70,13 +73,9 @@ static int __ib_process_cq(struct ib_cq *cq, int
> >> budget, struct ib_wc *wcs, {
> >> int i, n, completed = 0;
> >>
> >> - /*
> >> - * budget might be (-1) if the caller does not
> >> - * want to bound this call, thus we need unsigned
> >> - * minimum here.
> >> - */
> >> - while ((n = ib_poll_cq(cq, min_t(u32, batch,
> >> - budget - completed), wcs)) > 0) {
> >> + trace_cq_process(cq);
> >> + while ((n = ib_poll_cq(cq, batch, wcs)) > 0) {
> > Before this change, on first attempt to poll the cq, it will poll for min(batch,
> budget).
> > With this change, it will poll for batch.
> > This is functional change than just adding the trace points.
> > I am not sure if this has any effect on the overall polling.
> > But it may be worth to keep such functional change in pre-patch which consist
> of this change, moving comment section, batch recalculation.
>
> Or find a way to add the trace point without the functional change.
>
>
:-) yes.
> >> + trace_cq_poll(cq, batch, n);
> >> for (i = 0; i < n; i++) {
> >> struct ib_wc *wc = &wcs[i];
> >>
> >> @@ -87,9 +86,15 @@ static int __ib_process_cq(struct ib_cq *cq, int
> >> budget, struct ib_wc *wcs,
> >> }
> >>
> >> completed += n;
> >> -
> >> if (n != batch || (budget != -1 && completed >= budget))
> >> break;
> >> +
> >> + /*
> >> + * budget might be (-1) if the caller does not
> >> + * want to bound this call, thus we need unsigned
> >> + * minimum here.
> >> + */
> >> + batch = min_t(u32, batch, budget - completed);
> >> }
> >>
> >> return completed;
> >> @@ -131,8 +136,10 @@ static int ib_poll_handler(struct irq_poll *iop,
> >> int
> >> budget)
> >> completed = __ib_process_cq(cq, budget, cq->wc, IB_POLL_BATCH);
> >> if (completed < budget) {
> >> irq_poll_complete(&cq->iop);
> >> - if (ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0)
> >> + if (ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0) {
> >> + trace_cq_reschedule(cq);
> >> irq_poll_sched(&cq->iop);
> >> + }
> >> }
> >>
> >> if (dim)
> >> @@ -143,6 +150,7 @@ static int ib_poll_handler(struct irq_poll *iop,
> >> int
> >> budget)
> >>
> >> static void ib_cq_completion_softirq(struct ib_cq *cq, void *private)
> >> {
> >> + trace_cq_schedule(cq);
> >> irq_poll_sched(&cq->iop);
> >> }
> >>
> >> @@ -162,6 +170,7 @@ static void ib_cq_poll_work(struct work_struct
> >> *work)
> >>
> >> static void ib_cq_completion_workqueue(struct ib_cq *cq, void
> >> *private) {
> >> + trace_cq_schedule(cq);
> >> queue_work(cq->comp_wq, &cq->work);
> >> }
> >>
> >> @@ -239,6 +248,7 @@ struct ib_cq *__ib_alloc_cq_user(struct ib_device
> >> *dev, void *private,
> >> goto out_destroy_cq;
> >> }
> >>
> >> + trace_cq_alloc(cq, comp_vector, poll_ctx);
> >> return cq;
> >>
> >> out_destroy_cq:
> >> @@ -304,6 +314,7 @@ void ib_free_cq_user(struct ib_cq *cq, struct
> >> ib_udata
> >> *udata)
> >> WARN_ON_ONCE(1);
> >> }
> >>
> >> + trace_cq_free(cq);
> >> rdma_restrack_del(&cq->res);
> >> cq->device->ops.destroy_cq(cq, udata);
> >> if (cq->dim)
> >> diff --git a/drivers/infiniband/core/trace.c
> >> b/drivers/infiniband/core/trace.c new file mode 100644 index
> >> 0000000..6c3514b
> >> --- /dev/null
> >> +++ b/drivers/infiniband/core/trace.c
> >> @@ -0,0 +1,14 @@
> >> +// SPDX-License-Identifier: GPL-2.0-only
> >> +/*
> >> + * Trace points for core RDMA functions.
> >> + *
> >> + * Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >> + *
> >> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> >> + */
> >> +
> >> +#define CREATE_TRACE_POINTS
> >> +
> >> +#include <rdma/ib_verbs.h>
> >> +
> >> +#include <trace/events/rdma_core.h>
> >> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index
> >> 6a47ba8..95a6bce 100644
> >> --- a/include/rdma/ib_verbs.h
> >> +++ b/include/rdma/ib_verbs.h
> >> @@ -1555,6 +1555,8 @@ struct ib_cq {
> >> };
> >> struct workqueue_struct *comp_wq;
> >> struct dim *dim;
> >> + ktime_t timestamp;
> >> + bool interrupt;
> > Its unclear when to update timestamp and interrupt. Comment will help.
>
> These are both updated only in the new trace points. Is more than that needed
> in a comment?
>
No. It wasn't clear to me that when to update the timestamp.
But I guess its obvious..
>
> >> /*
> >> * Implementation details of the RDMA core, don't use in drivers:
> >> */
> >> diff --git a/include/trace/events/rdma_core.h
> >> b/include/trace/events/rdma_core.h
> >> new file mode 100644
> >> index 0000000..c1397a3
> >> --- /dev/null
> >> +++ b/include/trace/events/rdma_core.h
> >> @@ -0,0 +1,218 @@
> >> +/* SPDX-License-Identifier: GPL-2.0-only */
> >> +/*
> >> + * Trace point definitions for core RDMA functions.
> >> + *
> >> + * Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >> + *
> >> + * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
> >> + */
> >> +
> >> +#undef TRACE_SYSTEM
> >> +#define TRACE_SYSTEM rdma_core
> >> +
> >> +#if !defined(_TRACE_RDMA_CORE_H) ||
> >> defined(TRACE_HEADER_MULTI_READ)
> >> +#define _TRACE_RDMA_CORE_H
> >> +
> >> +#include <linux/tracepoint.h>
> >> +#include <rdma/ib_verbs.h>
> >> +#include <rdma/restrack.h>
> >> +
> >> +/*
> >> + * enum ib_poll_context, from include/rdma/ib_verbs.h */
> >> +#define IB_POLL_CTX_LIST \
> >> + ib_poll_ctx(DIRECT) \
> >> + ib_poll_ctx(SOFTIRQ) \
> >> + ib_poll_ctx(WORKQUEUE) \
> >> + ib_poll_ctx_end(UNBOUND_WORKQUEUE)
> >> +
> >> +#undef ib_poll_ctx
> >> +#undef ib_poll_ctx_end
> >> +
> >> +#define ib_poll_ctx(x) TRACE_DEFINE_ENUM(IB_POLL_##x);
> >> +#define ib_poll_ctx_end(x) TRACE_DEFINE_ENUM(IB_POLL_##x);
> >> +
> >> +IB_POLL_CTX_LIST
> >> +
> >> +#undef ib_poll_ctx
> >> +#undef ib_poll_ctx_end
> >> +
> >> +#define ib_poll_ctx(x) { IB_POLL_##x, #x },
> >> +#define ib_poll_ctx_end(x) { IB_POLL_##x, #x }
> >> +
> >> +#define rdma_show_ib_poll_ctx(x) \
> >> + __print_symbolic(x, IB_POLL_CTX_LIST)
> >> +
> >> +/**
> >> + ** Completion Queue events
> >> + **/
> >> +
> >> +TRACE_EVENT(cq_schedule,
> >> + TP_PROTO(
> >> + struct ib_cq *cq
> >> + ),
> >> +
> >> + TP_ARGS(cq),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + cq->timestamp = ktime_get();
> >> + cq->interrupt = true;
> >> +
> >> + __entry->id = cq->res.id;
> >> + ),
> >> +
> >> + TP_printk("id %u", __entry->id)
> >> +);
> >> +
> >> +TRACE_EVENT(cq_reschedule,
> >> + TP_PROTO(
> >> + struct ib_cq *cq
> >> + ),
> >> +
> >> + TP_ARGS(cq),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + cq->timestamp = ktime_get();
> >> + cq->interrupt = false;
> >> +
> >> + __entry->id = cq->res.id;
> >> + ),
> >> +
> >> + TP_printk("id %u", __entry->id)
> >> +);
> >> +
> >> +TRACE_EVENT(cq_process,
> >> + TP_PROTO(
> >> + const struct ib_cq *cq
> >> + ),
> >> +
> >> + TP_ARGS(cq),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(s64, latency)
> >> + __field(u32, id)
> >> + __field(bool, interrupt)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + ktime_t latency = ktime_sub(ktime_get(), cq->timestamp);
> >> +
> >> + __entry->id = cq->res.id;
> >> + __entry->latency = ktime_to_us(latency);
> >> + __entry->interrupt = cq->interrupt;
> >> + ),
> >> +
> >> + TP_printk("id %u wake-up took %lld [us] from %s",
> > It might be better to prefix 'id' with 'cq', so that in future rdma wide trace
> points, we can have multiple resource id's printed consistently as qpid, cqid,
> mrid etc; and don't have to rely on the function where it is used to decode what
> that id means.
>
> I left out the "cq" here because the trace point names are prefixed with "cq_".
> However, now that you bring it up, I can imagine cases where a trace point
> might report information about two different resources that both have a
> restrack ID.
>
> How about "cq.id=%u" ?
>
Looks good.
>
> > I had mixed thoughts on whether to pass ib_cq* or rdma_restrack_entry*.
> > I was thinking of rdma_restrack_entry*, as it makes future code for other
> resources also anchored on the resource id.
>
> On the other hand, a trace point might someday want to report the value of a
> field in struct ib_cq.
>
Yes. that is exactly why I had mix thoughts. So I think ib_cq is ok.
>
> >> + __entry->id, __entry->latency,
> >> + __entry->interrupt ? "interrupt" : "reschedule"
> >> + )
> >> +);
> >> +
> >> +TRACE_EVENT(cq_poll,
> >> + TP_PROTO(
> >> + const struct ib_cq *cq,
> >> + int requested,
> >> + int rc
> >> + ),
> >> +
> >> + TP_ARGS(cq, requested, rc),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + __field(int, requested)
> >> + __field(int, rc)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->id = cq->res.id;
> >> + __entry->requested = requested;
> >> + __entry->rc = rc;
> >> + ),
> >> +
> >> + TP_printk("id %u requested %d, returned %d",
> >> + __entry->id, __entry->requested, __entry->rc
> >> + )
> >> +);
> >> +
> >> +TRACE_EVENT(cq_modify,
> >> + TP_PROTO(
> >> + const struct ib_cq *cq,
> >> + u16 comps,
> >> + u16 usec
> >> + ),
> >> +
> >> + TP_ARGS(cq, comps, usec),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + __field(unsigned int, comps)
> >> + __field(unsigned int, usec)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->id = cq->res.id;
> >> + __entry->comps = comps;
> >> + __entry->usec = usec;
> >> + ),
> >> +
> >> + TP_printk("id %u comps=%u usec=%u",
> >> + __entry->id, __entry->comps, __entry->usec
> >> + )
> >> +);
> >> +
> >> +TRACE_EVENT(cq_alloc,
> >> + TP_PROTO(
> >> + const struct ib_cq *cq,
> >> + int comp_vector,
> >> + enum ib_poll_context poll_ctx
> >> + ),
> >> +
> >> + TP_ARGS(cq, comp_vector, poll_ctx),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + __field(int, comp_vector)
> >> + __field(unsigned long, poll_ctx)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->id = cq->res.id;
> >> + __entry->comp_vector = comp_vector;
> >> + __entry->poll_ctx = poll_ctx;
> >> + ),
> >> +
> >> + TP_printk("id %u comp_vector=%d poll_ctx=%s",
> >> + __entry->id, __entry->comp_vector,
> >> + rdma_show_ib_poll_ctx(__entry->poll_ctx)
> >> + )
> >> +);
> >> +
> >> +TRACE_EVENT(cq_free,
> >> + TP_PROTO(
> >> + const struct ib_cq *cq
> >> + ),
> >> +
> >> + TP_ARGS(cq),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field(u32, id)
> >> + ),
> >> +
> >> + TP_fast_assign(
> >> + __entry->id = cq->res.id;
> >> + ),
> >> +
> >> + TP_printk("id %u", __entry->id)
> >> +);
> >> +
> >> +#endif /* _TRACE_RDMA_CORE_H */
> >> +
> >> +#include <trace/define_trace.h>
>
> --
> Chuck Lever
>
>
