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    SubjectRe: Re: [PATCH v6 09/14] mm/damon: Add a tracepoint for result writing
    Date
    On Tue, 10 Mar 2020 09:03:31 +0000 Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:

    > On Mon, 24 Feb 2020 13:30:42 +0100
    > SeongJae Park <sjpark@amazon.com> wrote:
    >
    > > From: SeongJae Park <sjpark@amazon.de>
    > >
    > > This commit adds a tracepoint for DAMON's result buffer writing. It is
    > > called for each writing of the DAMON results and print the result data.
    > > Therefore, it would be used to easily integrated with other tracepoint
    > > supporting tracers such as perf.
    > >
    > > Signed-off-by: SeongJae Park <sjpark@amazon.de>
    >
    > I'm curious, why at the flush of rbuf rather than using a more structured trace
    > point for each of the writes into rbuf?
    >
    > Seems it would make more sense to have a tracepoint for each record write out.
    > Probably at the level of each task, though might be more elegant to do it at the
    > level of each region within a task and duplicate the header stuff.

    I was worried if the format changes, but agree your suggestion is the right
    way. Will change so in next spin.


    Thanks,
    SeongJae Park

    >
    > > ---
    > > include/trace/events/damon.h | 32 ++++++++++++++++++++++++++++++++
    > > mm/damon.c | 4 ++++
    > > 2 files changed, 36 insertions(+)
    > > create mode 100644 include/trace/events/damon.h
    > >
    > > diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h
    > > new file mode 100644
    > > index 000000000000..fb33993620ce
    > > --- /dev/null
    > > +++ b/include/trace/events/damon.h
    > > @@ -0,0 +1,32 @@
    > > +/* SPDX-License-Identifier: GPL-2.0 */
    > > +#undef TRACE_SYSTEM
    > > +#define TRACE_SYSTEM damon
    > > +
    > > +#if !defined(_TRACE_DAMON_H) || defined(TRACE_HEADER_MULTI_READ)
    > > +#define _TRACE_DAMON_H
    > > +
    > > +#include <linux/types.h>
    > > +#include <linux/tracepoint.h>
    > > +
    > > +TRACE_EVENT(damon_write_rbuf,
    > > +
    > > + TP_PROTO(void *buf, const ssize_t sz),
    > > +
    > > + TP_ARGS(buf, sz),
    > > +
    > > + TP_STRUCT__entry(
    > > + __dynamic_array(char, buf, sz)
    > > + ),
    > > +
    > > + TP_fast_assign(
    > > + memcpy(__get_dynamic_array(buf), buf, sz);
    > > + ),
    > > +
    > > + TP_printk("dat=%s", __print_hex(__get_dynamic_array(buf),
    > > + __get_dynamic_array_len(buf)))
    > > +);
    > > +
    > > +#endif /* _TRACE_DAMON_H */
    > > +
    > > +/* This part must be outside protection */
    > > +#include <trace/define_trace.h>
    > > diff --git a/mm/damon.c b/mm/damon.c
    > > index facb1d7f121b..8faf3879f99e 100644
    > > --- a/mm/damon.c
    > > +++ b/mm/damon.c
    > > @@ -9,6 +9,8 @@
    > >
    > > #define pr_fmt(fmt) "damon: " fmt
    > >
    > > +#define CREATE_TRACE_POINTS
    > > +
    > > #include <linux/damon.h>
    > > #include <linux/debugfs.h>
    > > #include <linux/delay.h>
    > > @@ -20,6 +22,7 @@
    > > #include <linux/sched/mm.h>
    > > #include <linux/sched/task.h>
    > > #include <linux/slab.h>
    > > +#include <trace/events/damon.h>
    > >
    > > #define damon_get_task_struct(t) \
    > > (get_pid_task(find_vpid(t->pid), PIDTYPE_PID))
    > > @@ -553,6 +556,7 @@ static void damon_flush_rbuffer(struct damon_ctx *ctx)
    > > */
    > > static void damon_write_rbuf(struct damon_ctx *ctx, void *data, ssize_t size)
    > > {
    > > + trace_damon_write_rbuf(data, size);
    > > if (!ctx->rbuf_len || !ctx->rbuf)
    > > return;
    > > if (ctx->rbuf_offset + size > ctx->rbuf_len)
    >

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