From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com,
peterz@infradead.org, oleg@redhat.com,
hegdevasant@linux.vnet.ibm.com, mingo@redhat.com,
anton@redhat.com, systemtap@sourceware.org,
aravinda@linux.vnet.ibm.com, penberg@iki.fi
Subject: Re: Re: [PATCH v4 5/5] perf/sdt: Add support to perf record to trace SDT events
Date: Tue, 04 Nov 2014 12:57:00 -0000 [thread overview]
Message-ID: <5458CD15.4010101@hitachi.com> (raw)
In-Reply-To: <54588905.7040002@linux.vnet.ibm.com>
Hi,
(2014/11/04 17:06), Hemant Kumar wrote:
> Hi Namhyung,
>
> On 11/04/2014 01:08 PM, Namhyung Kim wrote:
>> Hi Hemant,
>>
>> As you know, you need to keep an eye on how (kprobes) event cache
>> patchset from Masami settles down. For those who aren't CC'ed, please
>> see the link below:
>>
>> https://lkml.org/lkml/2014/10/31/207
>>
>> On Sun, 02 Nov 2014 16:26:28 +0530, Hemant Kumar wrote:
>>> This patch adds support to perf to record SDT events. When invoked,
>>> the SDT event is looked up in the sdt-cache. If its found, an entry is
>>> made silently to uprobe_events file and then recording is invoked, and
>>> then the entry for the SDT event in uprobe_events is silently discarded.
>>>
>>> The SDT events are already stored in a cache file
>>> (/var/cache/perf/perf-sdt-file.cache).
>>> Although the file_hash table helps in addition or deletion of SDT events
>>> from the cache, its not of much use when it comes to probing the actual
>>> SDT event, because the key to this hash list is a file name and not the
>>> SDT event name (which is given as an argument to perf record). So, we
>>> won't be able to hash into it.
>> It likely to be ended up with per-file or per-buildid cache files under
>> ~/.debug directory. In this case we also need to have the (central)
>> event-to-cache table anyway IMHO.
What we are talking is to make a new caching file with buildid under
.debug/.
We already has ~/.debug/.build-id/<build-id> for string the binary
symbol maps. I think there are 2 options, one is expanding the current
build-id file format to include sdt and probe-event caches. The other is
to add ~/.debug/.build-id/<build-id>.probe and
~/.debug/.build-id/<build-id>.sdt for caching probe/sdt information.
And also, user interface is a discussion point. This series defines new
sdt-cache command, and we already have buildid-cache command. We should
have probe-cache command too? or consolidate those cache managing commands?
This question should be involving your series too.
>>> To avoid this problem, we can create another hash list "event_hash" list
>>> which will be maintained along with the file_hash list.
>>> Whenever a user invokes 'perf record -e %provider:event, perf should
>>> initialize the event_hash list and the file_hash list.
>>> The key to event_hash list is calculated from the event name and its
>>> provider name.
>> Isn't it enough just to use provide name? I guess the provider names
>> are (should be?) unique among a system although there's no absolute
>> guarantee for that.
>>
>
> Yes, there is no guarantee for the provider names to be unique.
> If we use only provider name with "perf record", then, what if a user
> wants to trace
> only a specific SDT event (not all the events for that provider)?
> What do you think?
How about failing if the provider name is not unique unless user
gives the actual binary path?
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2014-11-04 12:57 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-02 12:40 [PATCH v4 0/5] perf/sdt: SDT events listing/probing Hemant Kumar
2014-11-02 12:41 ` [PATCH v4 1/5] perf/sdt: ELF support for SDT Hemant Kumar
2014-11-02 12:42 ` [PATCH v4 2/5] perf/sdt: Add SDT events into a cache Hemant Kumar
2014-11-02 12:42 ` [PATCH v4 3/5] perf/sdt: Show SDT cache contents Hemant Kumar
2014-11-02 12:42 ` [PATCH v4 4/5] perf/sdt: Delete SDT events from cache Hemant Kumar
2014-11-02 12:43 ` [PATCH v4 5/5] perf/sdt: Add support to perf record to trace SDT events Hemant Kumar
2014-11-04 7:38 ` Namhyung Kim
2014-11-04 8:06 ` Hemant Kumar
2014-11-04 12:57 ` Masami Hiramatsu [this message]
[not found] ` <5459BD3E.7010804@linux.vnet.ibm.com>
2014-11-05 6:51 ` Re: " Hemant Kumar
2014-11-05 9:07 ` Masami Hiramatsu
2014-11-05 13:28 ` Arnaldo Carvalho de Melo
2014-11-05 7:06 ` Namhyung Kim
2014-11-05 9:05 ` Masami Hiramatsu
2014-11-06 2:16 ` Josh Stone
2014-11-06 5:34 ` Masami Hiramatsu
2014-11-06 7:06 ` Hemant Kumar
2014-11-06 14:56 ` Masami Hiramatsu
2014-11-07 8:21 ` [RFC] perf-cache command interface design Masami Hiramatsu
2014-11-07 8:42 ` Peter Zijlstra
2014-11-07 13:58 ` [PATCH RESEND 1/2] perf tools: Move disable_buildid_cache() to util/build-id.c Namhyung Kim
2014-11-07 13:58 ` [PATCH 2/2] perf tools: Add record.use-buildid-cache config option Namhyung Kim
2014-11-07 15:16 ` [RFC] perf-cache command interface design David Ahern
2014-11-07 15:33 ` Arnaldo Carvalho de Melo
2014-11-07 10:51 ` Hemant Kumar
2014-11-08 4:15 ` Masami Hiramatsu
2014-11-07 14:38 ` Arnaldo Carvalho de Melo
2014-11-08 4:26 ` Masami Hiramatsu
2014-11-07 14:43 ` Namhyung Kim
2014-11-08 4:38 ` Masami Hiramatsu
2014-11-10 10:59 ` Masami Hiramatsu
2014-11-10 12:23 ` Arnaldo Carvalho de Melo
2014-11-11 6:53 ` Masami Hiramatsu
2014-11-11 13:10 ` Arnaldo Carvalho de Melo
2014-11-12 15:26 ` Masami Hiramatsu
2014-11-17 3:09 ` Namhyung Kim
2014-11-17 3:17 ` Masami Hiramatsu
2014-11-17 22:09 ` Masami Hiramatsu
2014-11-18 4:51 ` Namhyung Kim
2014-11-18 11:16 ` Masami Hiramatsu
2014-11-18 4:41 ` Namhyung Kim
2014-11-18 10:32 ` Masami Hiramatsu
2014-11-17 18:59 ` Arnaldo Carvalho de Melo
2014-11-18 4:46 ` Namhyung Kim
2014-11-10 12:05 ` Hagen Paul Pfeifer
2014-11-10 12:31 ` Arnaldo Carvalho de Melo
2014-11-10 12:50 ` Peter Zijlstra
2014-11-10 13:37 ` Hagen Paul Pfeifer
2014-11-05 18:24 ` [PATCH v4 5/5] perf/sdt: Add support to perf record to trace SDT events Hemant Kumar
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