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Date: Fri, 26 Aug 2005 16:05:50 -0700 (PDT)
From: Christoph Lameter <clameter@engr.sgi.com>
To: Rusty Lynch <rusty.lynch@intel.com>
cc: linux-mm@kvack.org, prasanna@in.ibm.com, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org, anil.s.keshavamurthy@intel.com
Subject: Re:[PATCH] Only process_die notifier in ia64_do_page_fault if KPROBES
 is configured.
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On Fri, 26 Aug 2005, Rusty Lynch wrote:

> Just to be sure everyone understands the overhead involved, kprobes only 
> registers a single notifier.  If kprobes is disabled (CONFIG_KPROBES is
> off) then the overhead on a page fault is the overhead to execute an empty
> notifier chain.

Its the overhead of using registers to pass parameters, performing a 
function call that does nothing etc. A waste of computing resources. All 
of that unconditionally in a performance critical execution path that 
is executed a gazillion times for an optional feature that I frankly 
find not useful at all and that is disabled by default.