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From: "K. Prasad" <prasad@linux.vnet.ibm.com>
To: dwilder@us.ibm.com
Cc: David Wilder <dwilder@us.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, systemtap@sourceware.org,
	prasadav@us.ibm.com, hch@infradead.org
Subject: Re: [PATCH 0/3] A kernel tracing interface
Date: Fri, 29 Feb 2008 17:38:32 +0530	[thread overview]
Message-ID: <20080229120832.GA4650@in.ibm.com> (raw)
In-Reply-To: <20080229053605.GA10497@in.ibm.com>

On Fri, Feb 29, 2008 at 11:06:05AM +0530, K. Prasad wrote:
> On Thu, Feb 28, 2008 at 11:40:21AM -0800, David Wilder wrote:
> > Andrew Morton wrote:
> > >On Tue, 26 Feb 2008 14:38:37 -0800 "David J. Wilder" <dwilder@us.ibm.com> 
> > >wrote:
> > >
> > >>These patches provide a kernel tracing interface called "trace".
> > >>
> > >>ChangeLog:
> > >>-Updated to 2.6.25-rc2-mm1
> > >>-Removed sem_watch example, to hard to maintain.
> > >>-Added a new example that demonstrates per-cpu continuous tracing
> > >> of data generated using marker probes.
> > >>-Removed inline from relay patch.
> > >>-Moved examples into /sample directory.
> > >>
> > >>The motivation for "trace" is to:
> > >>- Provide a simple set of tracing primitives that will utilize the high-
> > >>  performance and low-overhead of relayfs for passing traces data from
> > >>  kernel to user space.
> > >>- Provide a common user interface for managing kernel traces.
> > >>- Allow for binary as well as ascii trace data.
> > >>- Incorporate features from the systemtap runtime that are
> > >>  useful to others.
> > >
> > >So... what's the story on this versus lttng?
> > 
> > Trace is simpler to use and a smaller bit of code than lttng.
> > It may not have all the features of lttng but it is good starting point 
> > that can be expanded upon.  I have several users of trace that just 
> > wanted a simple way to get data out of the kernel without the overhead 
> > of lttng trace is working well for them.  Trace also works well with 
> > markers and kprobes.  For example systemtap is is using the basic trace 
> > code to gather data from kprobes and markers.
> > >
> > >Is there some userspace code available for people to test this?  Maybe it's
> > >mentioned and I missed it.
> > 
> > I purposely designed trace so no special user code is required to gather 
> > trace data. Standard user utilities like cat, grep, sort and more is all 
> > that is needed.  I show an example in /samples/trace/fork_trace.c.
> > 
> > However since trace uses relay as its transport any user interfaces 
> > provided by relay can be used to read trace data. (documented in 
> > /Documentation/relay.txt)
> > 
> > >
> > >It'd be interesting to see a writeup of the proposed kernel<->userspace
> > >interfaces.  I see a description of kernel-internal interfaces, but how do
> > >users use it?
> > 
> > I will add some text in the documentation.
> > >
> > >I see it uses things from blktrace.  Can blktrace be switched over to being
> > >a client of this code?
> > 
> > yep.
> >
> Dave,
> 	I might also want to add to the discussion by stating that you
> will find a user for the 'trace' infrastructure in the marker handler 
> code of the proposed markers for futex subsystem. I hope to post the 
> patches soon to the community.
>
Also to let you know that I tested the patches (sent against
2.6.25-rc2-mm1) on a x86 machine and they've been working fine....

Thanks,
K.Prasad


  reply	other threads:[~2008-02-29 12:08 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-26 22:38 David J. Wilder
2008-02-28 10:04 ` Andrew Morton
2008-02-28 19:40   ` David Wilder
2008-02-29  5:36     ` K. Prasad
2008-02-29 12:08       ` K. Prasad [this message]
  -- strict thread matches above, loose matches on Subject: below --
2007-11-13  1:02 David J. Wilder
2007-10-02 18:55 David J. Wilder
2007-10-02 16:33 David J. Wilder

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