From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: kys@microsoft.com, linux-kernel@vger.kernel.org,
devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com,
jasowang@redhat.com, leann.ogasawara@canonical.com,
marcelo.cerri@canonical.com, sthemmin@microsoft.com,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 10/17] hyper-v: trace vmbus_open()
Date: Mon, 30 Oct 2017 11:07:01 +0100 [thread overview]
Message-ID: <873761ymnu.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20171030084537.GA14865@kroah.com> (Greg KH's message of "Mon, 30 Oct 2017 09:45:37 +0100")
Greg KH <gregkh@linuxfoundation.org> writes:
> On Mon, Oct 30, 2017 at 09:16:19AM +0100, Vitaly Kuznetsov wrote:
>> Greg KH <gregkh@linuxfoundation.org> writes:
>>
>> > On Sun, Oct 29, 2017 at 12:21:09PM -0700, kys@exchange.microsoft.com wrote:
>> >> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>> >>
>> >> Add tracepoint to CHANNELMSG_OPENCHANNEL sender.
>> >>
>> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> >> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
>> >> ---
>> >> drivers/hv/channel.c | 2 ++
>> >> drivers/hv/hv_trace.h | 27 +++++++++++++++++++++++++++
>> >> 2 files changed, 29 insertions(+)
>> >>
>> >> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
>> >> index a406beb10dd0..739b3fe1e0fb 100644
>> >> --- a/drivers/hv/channel.c
>> >> +++ b/drivers/hv/channel.c
>> >> @@ -185,6 +185,8 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
>> >> ret = vmbus_post_msg(open_msg,
>> >> sizeof(struct vmbus_channel_open_channel), true);
>> >>
>> >> + trace_vmbus_open(open_msg, ret);
>> >
>> > Why add tracepoints for things that ftrace can handle automatically?
>>
>> This series adds pretty prints for structures printing what is needed
>> and in the right format significantly simplifying debugging. And it
>> wouldn't make sense to add tracepoints to *some* messages-related
>> functions and skip others where parsing is more trivial.
>
> Tracepoints add memory usage and take up real space. If you don't need
> them for something, as there are other ways to already get the
> information needed, why add new ones that you now need to drag around
> for all time?
>
Are you opposed to the series as a whole (AKA 'no tracepoints in
drivers') or only to some tracepoints we add here?
Debugging stuff is always a tradeof between some memory overhead and
convenience (and CONFIG_TRACEPOINTS is the knob). Here I'd like to see
vmbus_* structures parsed in output. When things go wrong I can tell
someone "do echo 1 > /sys/kernel/debug/tracing/events/hyperv/enable and
show me the output" and I will have enough information to figure out
what's going on.
I'm probably missing something about easy 'alternative' ways to get what
I need and why people add tracepoints to drivers in general.
--
Vitaly
next prev parent reply other threads:[~2017-10-30 10:07 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-29 19:20 [PATCH 00/17] Drivers: hv: vmbus: Add tracing to VMBus kys
2017-10-29 19:21 ` [PATCH 01/17] hyper-v: trace vmbus_on_msg_dpc() kys
2017-10-29 19:21 ` [PATCH 02/17] hyper-v: trace vmbus_on_message() kys
2017-10-29 19:21 ` [PATCH 03/17] hyper-v: trace vmbus_onoffer() kys
2017-10-29 19:21 ` [PATCH 04/17] hyper-v: trace vmbus_onoffer_rescind() kys
2017-10-29 19:21 ` [PATCH 05/17] hyper-v: trace vmbus_onopen_result() kys
2017-10-29 19:21 ` [PATCH 06/17] hyper-v: trace vmbus_ongpadl_created() kys
2017-10-29 19:21 ` [PATCH 07/17] hyper-v: trace vmbus_ongpadl_torndown() kys
2017-10-29 19:21 ` [PATCH 08/17] hyper-v: trace vmbus_onversion_response() kys
2017-10-29 19:21 ` [PATCH 09/17] hyper-v: trace vmbus_request_offers() kys
2017-10-29 19:21 ` [PATCH 10/17] hyper-v: trace vmbus_open() kys
2017-10-29 20:59 ` Greg KH
2017-10-30 8:16 ` Vitaly Kuznetsov
2017-10-30 8:45 ` Greg KH
2017-10-30 10:07 ` Vitaly Kuznetsov [this message]
2017-10-30 10:32 ` Greg KH
2017-10-30 14:31 ` Steven Rostedt
2017-10-31 12:48 ` Greg KH
2017-10-31 13:10 ` Steven Rostedt
2017-11-01 17:43 ` KY Srinivasan
2017-11-04 11:05 ` Greg KH
2017-11-04 15:09 ` KY Srinivasan
2017-10-31 17:41 ` Stephen Hemminger
2017-10-29 19:21 ` [PATCH 11/17] hyper-v: trace vmbus_close_internal() kys
2017-10-29 19:21 ` [PATCH 12/17] hyper-v: trace vmbus_establish_gpadl() kys
2017-10-29 19:21 ` [PATCH 13/17] hyper-v: trace vmbus_teardown_gpadl() kys
2017-10-29 19:21 ` [PATCH 14/17] hyper-v: trace vmbus_negotiate_version() kys
2017-10-29 19:21 ` [PATCH 15/17] hyper-v: trace vmbus_release_relid() kys
2017-10-29 19:21 ` [PATCH 16/17] hyper-v: trace vmbus_send_tl_connect_request() kys
2017-10-29 19:21 ` [PATCH 17/17] hyper-v: trace channel events kys
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