linux-kernel - Re: [PATCH] interconnect: Add basic tracepoints

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Date:   Fri, 18 Oct 2019 10:13:42 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Georgi Djakov <georgi.djakov@...aro.org>
Cc:     linux-pm@...r.kernel.org, mingo@...hat.com,
        bjorn.andersson@...aro.org, vincent.guittot@...aro.org,
        daidavid1@...eaurora.org, okukatla@...eaurora.org,
        evgreen@...omium.org, mka@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] interconnect: Add basic tracepoints

On Fri, 18 Oct 2019 17:02:24 +0300
Georgi Djakov <georgi.djakov@...aro.org> wrote:

> The tracepoints can help with understanding the system behavior of a
> given interconnect path when the consumer drivers change their bandwidth
> demands. This might be interesting when we want to monitor the requested
> interconnect bandwidth for each client driver. The paths may share the
> same nodes and this will help to understand "who and when is requesting
> what". All this is useful for subsystem drivers developers and may also
> provide hints when optimizing the power and performance profile of the
> system.
> 
> Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
> ---
>  MAINTAINERS                         |  1 +
>  drivers/interconnect/core.c         |  9 +++++
>  include/trace/events/interconnect.h | 52 +++++++++++++++++++++++++++++
>  3 files changed, 62 insertions(+)
>  create mode 100644 include/trace/events/interconnect.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 55199ef7fa74..c307c4b8f677 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8526,6 +8526,7 @@ F:	drivers/interconnect/
>  F:	include/dt-bindings/interconnect/
>  F:	include/linux/interconnect-provider.h
>  F:	include/linux/interconnect.h
> +F:	include/trace/events/interconnect.h
>  
>  INVENSENSE MPU-3050 GYROSCOPE DRIVER
>  M:	Linus Walleij <linus.walleij@...aro.org>
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index 7b971228df38..e24092558c29 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -24,6 +24,9 @@ static LIST_HEAD(icc_providers);
>  static DEFINE_MUTEX(icc_lock);
>  static struct dentry *icc_debugfs_dir;
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/interconnect.h>
> +
>  /**
>   * struct icc_req - constraints that are attached to each node
>   * @req_node: entry in list of requests for the particular @node
> @@ -449,6 +452,9 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
>  
>  		/* aggregate requests for this node */
>  		aggregate_requests(node);
> +
> +		trace_icc_set_bw(node, dev_name(path->reqs[i].dev),
> +				 avg_bw, peak_bw);

BTW, it's best to do the "dev_name()" from the TP_fast_assign()
portion. It keeps the work out of the inlined code here. Although it
shouldn't be processed within the fast path, it still adds a cache
footprint.

		trace_icc_set_bw(node, path->reqs[i].dev, avg_bw, peak_bw);

>  	}
>  
>  	ret = apply_constraints(path);
> @@ -461,6 +467,9 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
>  			path->reqs[i].avg_bw = old_avg;
>  			path->reqs[i].peak_bw = old_peak;
>  			aggregate_requests(node);
> +
> +			trace_icc_set_bw(node, dev_name(path->reqs[i].dev),
> +					 old_avg, old_peak);
>  		}
>  		apply_constraints(path);
>  	}
> diff --git a/include/trace/events/interconnect.h b/include/trace/events/interconnect.h
> new file mode 100644
> index 000000000000..8e001382e9b0
> --- /dev/null
> +++ b/include/trace/events/interconnect.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2019, Linaro Ltd.
> + * Author: Georgi Djakov <georgi.djakov@...aro.org>
> + */
> +
> +#if !defined(_TRACE_INTERCONNECT_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_INTERCONNECT_H
> +
> +#include <linux/tracepoint.h>
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM interconnect
> +
> +struct icc_node;
> +
> +TRACE_EVENT(icc_set_bw,
> +
> +	TP_PROTO(struct icc_node *n, const char *cdev, u32 avg_bw, u32 peak_bw),

	TP_PROTO(struct icc_node *n, const struct device *cdev,

> +
> +	TP_ARGS(n, cdev, avg_bw, peak_bw),
> +
> +	TP_STRUCT__entry(
> +		__string(node_name, n->name)
> +		__field(u32, node_avg_bw)
> +		__field(u32, node_peak_bw)
> +		__string(cdev, cdev)

		__string(cdev, dev_name(cdev))

> +		__field(u32, avg_bw)
> +		__field(u32, peak_bw)
> +	),
> +
> +	TP_fast_assign(
> +		__assign_str(node_name, n->name);
> +		__entry->node_avg_bw = n->avg_bw;
> +		__entry->node_peak_bw = n->peak_bw;
> +		__assign_str(cdev, cdev);

		__assign_str(cdev, dev_name(cdev));

-- Steve

> +		__entry->avg_bw = avg_bw;
> +		__entry->peak_bw = peak_bw;
> +	),
> +
> +	TP_printk("%s avg_bw=%u peak_bw=%u cdev=%s avg_bw=%u peak_bw=%u",
> +		__get_str(node_name),
> +		__entry->node_avg_bw,
> +		__entry->node_peak_bw,
> +		__get_str(cdev),
> +		__entry->avg_bw,
> +		__entry->peak_bw)
> +);
> +#endif /* _TRACE_INTERCONNECT_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>