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Re: [RFC]-Approaches to user space probes
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: prasanna at in dot ibm dot com
- Cc: suparna at in dot ibm dot com, ak at suse dot de, roland at redhat dot com, anil dot s dot keshavamurthy at intel dot com, varap at us dot ibm dot com, systemtap at sources dot redhat dot com
- Date: 01 Feb 2006 18:06:21 -0500
- Subject: Re: [RFC]-Approaches to user space probes
- References: <20060127121847.GA4926@in.ibm.com>
prasanna wrote:
> 1. Attaching or loading the application into the tool.
> 2. Using a jump instruction to a trampoline and trampoline
> executing the instrumented code.
> 3. Using a breakpoint instruction and changing the instruction
> point to the instrumentaiton code which is part of user
> address space.
> 4. Using a breakpoint instruction and executing the
> instrumentation code within the breakpoint handler.
> [...]
Very early on in the project, I had imagined something like #1-3, but
since have come to a conclusion that #4 makes the most sense. Josh's
reason (correlating user & kernel side events) is one; invisibility to
the user-space program is another, and related to that, less
likelihood of interference with complex programs (signals, threading);
simplicity of concurrency rules (atomic probe handlers).
- FChE