From: David Daney <ddaney@caviumnetworks.com>
To: "Ted Ts'o" <tytso@mit.edu>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: Perf can't deal with many tracepoints
Date: Wed, 27 Oct 2010 17:45:50 -0700 [thread overview]
Message-ID: <4CC8C7BE.4010102@caviumnetworks.com> (raw)
In-Reply-To: <20101028004047.GH3194@thunk.org>
On 10/27/2010 05:40 PM, Ted Ts'o wrote:
> On Wed, Oct 27, 2010 at 05:16:18PM -0700, David Daney wrote:
>> Tracing is supposed to be low overhead. Forcing people to decode
>> things like this at the trace point, may take more code and cause
>> the trace data to be larger, making it slower than necessary.
>>
>> If there isn't a good reason to keep perf stupid, then making it
>> smarter could be attractive.
>
> Agreed. Although one argument against making perf smarter is that
> certain things such as the dev_t MAJOR/MINOR split is an internal
> abstraction that could potentially vary from kernel to kernel.
>
> And the question is whether perf really should be so different that if
> you boot a different kernel, you had better have the right perf
> installed.
>
It may be possible to encode the dev_t split in the trace meta-data.
This is done for some other types. Then perf could decode it based on
the meta-data.
Another option is to have perf print the raw data and not crash. Then
someone looking at the output could, if they desired, decode the dev_t
themselves.
David Daney
next prev parent reply other threads:[~2010-10-28 0:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-27 23:20 Perf can't deal with many tracepoints Theodore Ts'o
2010-10-28 0:16 ` David Daney
2010-10-28 0:40 ` Ted Ts'o
2010-10-28 0:45 ` David Daney [this message]
2010-10-28 17:42 ` Frank Ch. Eigler
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