From: Steven Rostedt <rostedt@goodmis.org>
To: Qais Yousef <qais.yousef@arm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Mel Gorman <mgorman@suse.de>,
Patrick Bellasi <patrick.bellasi@matbug.net>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Randy Dunlap <rdunlap@infradead.org>,
Jonathan Corbet <corbet@lwn.net>,
Juri Lelli <juri.lelli@redhat.com>,
Ben Segall <bsegall@google.com>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Quentin Perret <qperret@google.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Pavan Kondeti <pkondeti@codeaurora.org>,
linux-doc@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-fs <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value
Date: Mon, 8 Jun 2020 10:44:24 -0400 [thread overview]
Message-ID: <20200608104424.10781990@gandalf.local.home> (raw)
In-Reply-To: <20200608123102.6sdhdhit7lac5cfl@e107158-lin.cambridge.arm.com>
On Mon, 8 Jun 2020 13:31:03 +0100
Qais Yousef <qais.yousef@arm.com> wrote:
> I admit I don't know how much of these numbers is ftrace overhead. When trying
Note, if you want to get a better idea of how long a function runs, put it
into set_ftrace_filter, and then trace it. That way you remove the overhead
of the function graph tracer when its nesting within a function.
> to capture similar runs for uclamp, the numbers didn't add up compared to
> running the test without ftrace generating the graph. If juno is suffering from
> bad branching costs in this path, then I suspect ftrace will amplify this as
> AFAIU it'll cause extra jumps on entry and exit.
>
>
>
> sched-pipe-6532 [001] 9407.276302: funcgraph_entry: | deactivate_task() {
> sched-pipe-6532 [001] 9407.276302: funcgraph_entry: | dequeue_task_fair() {
> sched-pipe-6532 [001] 9407.276303: funcgraph_entry: | update_curr() {
> sched-pipe-6532 [001] 9407.276304: funcgraph_entry: 0.780 us | update_min_vruntime();
> sched-pipe-6532 [001] 9407.276306: funcgraph_entry: | cpuacct_charge() {
> sched-pipe-6532 [001] 9407.276306: funcgraph_entry: 0.820 us | __rcu_read_lock();
> sched-pipe-6532 [001] 9407.276308: funcgraph_entry: 0.740 us | __rcu_read_unlock();
The above is more accurate than...
> sched-pipe-6532 [001] 9407.276309: funcgraph_exit: 3.980 us | }
this one. Because this one has nested tracing within it.
-- Steve
> sched-pipe-6532 [001] 9407.276310: funcgraph_entry: 0.720 us | __rcu_read_lock();
> sched-pipe-6532 [001] 9407.276312: funcgraph_entry: 0.720 us | __rcu_read_unlock();
> sched-pipe-6532 [001] 9407.276313: funcgraph_exit: 9.840 us | }
> sched-pipe-6532 [001] 9407.276314: funcgraph_entry: | __update_load_avg_se() {
> sched-pipe-6532 [001] 9407.276315: funcgraph_entry: 0.720 us | __accumulate_pelt_segments();
> sched-pipe-6532 [001] 9407.276316: funcgraph_exit: 2.260 us | }
> sched-pipe-6532 [001] 9407.276317: funcgraph_entry: | __update_load_avg_cfs_rq() {
> sched-pipe-6532 [001] 9407.276318: funcgraph_entry: 0.860 us | __accumulate_pelt_segments();
> sched-pipe-6532 [001] 9407.276319: funcgraph_exit: 2.340 us | }
next prev parent reply other threads:[~2020-06-08 14:44 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 15:40 [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value Qais Yousef
2020-05-11 15:40 ` [PATCH 2/2] Documentation/sysctl: Document uclamp sysctl knobs Qais Yousef
2020-05-11 17:18 ` [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value Qais Yousef
2020-05-12 2:10 ` Pavan Kondeti
2020-05-12 11:46 ` Qais Yousef
2020-05-15 11:08 ` Patrick Bellasi
2020-05-18 8:31 ` Dietmar Eggemann
2020-05-18 16:49 ` Qais Yousef
2020-05-28 13:23 ` Peter Zijlstra
2020-05-28 15:58 ` Qais Yousef
2020-05-28 16:11 ` Peter Zijlstra
2020-05-28 16:51 ` Qais Yousef
2020-05-28 18:29 ` Peter Zijlstra
2020-05-28 19:08 ` Patrick Bellasi
2020-05-28 19:20 ` Dietmar Eggemann
2020-05-29 9:11 ` Qais Yousef
2020-05-29 10:21 ` Mel Gorman
2020-05-29 15:11 ` Qais Yousef
2020-05-29 16:02 ` Mel Gorman
2020-05-29 16:05 ` Qais Yousef
2020-05-29 10:08 ` Mel Gorman
2020-05-29 16:04 ` Qais Yousef
2020-05-29 16:57 ` Mel Gorman
2020-06-02 16:46 ` Dietmar Eggemann
2020-06-03 8:29 ` Patrick Bellasi
2020-06-03 10:10 ` Mel Gorman
2020-06-03 14:59 ` Vincent Guittot
2020-06-03 16:52 ` Qais Yousef
2020-06-04 12:14 ` Vincent Guittot
2020-06-05 10:45 ` Qais Yousef
2020-06-09 15:29 ` Vincent Guittot
2020-06-08 12:31 ` Qais Yousef
2020-06-08 13:06 ` Valentin Schneider
2020-06-08 14:44 ` Steven Rostedt [this message]
2020-06-11 10:13 ` Qais Yousef
2020-06-09 17:10 ` Vincent Guittot
2020-06-11 10:24 ` Qais Yousef
2020-06-11 12:01 ` Vincent Guittot
2020-06-23 15:44 ` Qais Yousef
2020-06-24 8:45 ` Vincent Guittot
2020-06-05 7:55 ` Patrick Bellasi
2020-06-05 11:32 ` Qais Yousef
2020-06-05 13:27 ` Patrick Bellasi
2020-06-03 9:40 ` Mel Gorman
2020-06-03 12:41 ` Qais Yousef
2020-06-04 13:40 ` Mel Gorman
2020-06-05 10:58 ` Qais Yousef
2020-06-11 10:58 ` Qais Yousef
2020-06-16 11:08 ` Qais Yousef
2020-06-16 13:56 ` Lukasz Luba
-- strict thread matches above, loose matches on Subject: below --
2020-04-03 12:30 Qais Yousef
2020-04-14 18:21 ` Patrick Bellasi
2020-04-15 7:46 ` Patrick Bellasi
2020-04-20 15:04 ` Qais Yousef
2020-04-20 8:24 ` Dietmar Eggemann
2020-04-20 15:19 ` Qais Yousef
2020-04-21 0:52 ` Steven Rostedt
2020-04-21 11:16 ` Dietmar Eggemann
2020-04-21 11:23 ` Qais Yousef
2020-04-20 14:50 ` Qais Yousef
2020-04-15 10:11 ` Quentin Perret
2020-04-20 15:08 ` Qais Yousef
2020-04-20 8:29 ` Dietmar Eggemann
2020-04-20 15:13 ` Qais Yousef
2020-04-21 11:18 ` Dietmar Eggemann
2020-04-21 11:27 ` Qais Yousef
2020-04-22 10:59 ` Dietmar Eggemann
2020-04-22 13:13 ` Qais Yousef
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