From: Tingwei Zhang <tingweiz@codeaurora.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: tsoni@codeaurora.org,
Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Tingwei Zhang <tingwei@codeaurora.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Mao Jinlong <jinlmao@codeaurora.org>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
linux-stm32@st-md-mailman.stormreply.com,
linux-arm-kernel@lists.infradead.org,
Alexandre Torgue <alexandre.torgue@st.com>
Subject: Re: [PATCH v3 6/6] stm class: ftrace: use different channel accroding to CPU
Date: Wed, 23 Sep 2020 12:39:07 +0800 [thread overview]
Message-ID: <20200923043907.GA5146@codeaurora.org> (raw)
In-Reply-To: <87zh5nw8vz.fsf@ashishki-desk.ger.corp.intel.com>
On Fri, Sep 18, 2020 at 08:45:52PM +0800, Alexander Shishkin wrote:
> Tingwei Zhang <tingwei@codeaurora.org> writes:
>
> > @@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
> > {
> > int ret;
> >
> > + stm_ftrace.data.nr_chans = num_possible_cpus();
>
> Not a problem with this patch necesarily, but this made me realize that
> .nr_chans may be larger than:
>
> (1) what the policy permits,
> (2) what the stm device can handle.
>
> While (1) the user can fix in the policy, they won't be able to fix (2),
> in which case they won't be able to use stm_ftrace at all. I'm thinking
> if a link-time callback would be good enough.
>
Hi Alex,
I'm not sure if I understand this correct. If the nr_chans requested by
stm_ftrace is larger than policy permits or stm device can handle,
stm_assign_first_policy() returns with error so stm_source_link_add()
will fail. User would notice that when link happens. There's not much
we can do if resource is not enough.
> Another thing is that .nr_chans needs to be a power of 2 at the moment.
>
I'll change to below.
stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
> Regards,
> --
> Alex
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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next prev parent reply other threads:[~2020-09-23 4:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 0:17 [PATCH v3 0/6] tracing: export event trace and trace_marker Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 1/6] stm class: ftrace: change dependency to TRACING Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 2/6] tracing: add flag to control different traces Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 3/6] tracing: add trace_export support for event trace Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 4/6] tracing: add trace_export support for trace_marker Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 5/6] stm class: ftrace: enable supported trace export flag Tingwei Zhang
2020-09-03 0:17 ` [PATCH v3 6/6] stm class: ftrace: use different channel accroding to CPU Tingwei Zhang
2020-09-18 12:45 ` Alexander Shishkin
2020-09-23 4:39 ` Tingwei Zhang [this message]
2020-09-14 23:27 ` [PATCH v3 0/6] tracing: export event trace and trace_marker Tingwei Zhang
2020-09-18 14:26 ` Alexander Shishkin
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