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Re: design: function-exit probes
- From: Maneesh Soni <maneesh at in dot ibm dot com>
- To: Jim Keniston <jkenisto at us dot ibm dot com>
- Cc: systemtap at sources dot redhat dot com
- Date: Tue, 15 Feb 2005 15:53:14 +0530
- Subject: Re: design: function-exit probes
- References: <1108400498.2621.11.camel@dyn318270bld.beaverton.ibm.com>
- Reply-to: maneesh at in dot ibm dot com
On Mon, Feb 14, 2005 at 09:01:38AM -0800, Jim Keniston wrote:
[..]
> maxactive is specified by the user. It is the number of instances of the
> probed function that can be active concurrently. For example, if the
> function is non-recusrive and is called with a spinlock or mutex held,
> maxactive = 1 should be enough. If the function never sleeps and is
> not recursive, NR_CPUS should be enough. (Right?) maxactive is used to
If I am not wrong, here we should keep kernel premption also in mind. So,
in addition to above conditions, maxactive will be NR_CPUS when premption
is disabled.
>
> 1.5 Assumptions and Limitations
>
> 1. This requires a probepoint (but not necessarily a user-defined
> handler) at the entry to every function whose returns are traced.
I think we need to take care for the case when user explicitly
wants to probe function entry point. I am not sure if kprobe
handles two probe handler for the same address.
Thanks
Maneesh
--
Maneesh Soni
Linux Technology Center,
IBM India Software Labs,
Bangalore, India
email: maneesh@in.ibm.com
Phone: 91-80-25044990