linux-kernel - Re: [patch 2/9] Conditional Calls

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Date:	Fri, 1 Jun 2007 12:46:23 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/9] Conditional Calls - Hash Table

* Matt Mackall (mpm@...enic.com) wrote:
> On Thu, May 31, 2007 at 03:42:50PM +0200, Andi Kleen wrote:
> > Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> writes:
> > 
> > > Reimplementation of the cond calls which uses a hash table to hold the active
> > > cond_calls. It permits to first arm a cond_call and then load supplementary
> > > modules that contain this cond_call.
> > 
> > Hash table is probably overkill. This is a very very slow path operation.
> > Can you simplify the code? Just a linked list of all the condcall segments
> > should be enough  and then walk it.
> 
> I think it could be greatly simplified by using symbols instead of
> strings.
> 
> That is, doing cond_call(foo, func()) rather than cond_call("foo",
> func()). Here foo is a structure or type holding the relevant info to
> deal with the cond_call infrastructure. For unoptimized architectures,
> it can simply be a bool, which will be faster.
> 
> This has the added advantage that the compiler will automatically pick
> up any misspellings of these things. And it saves the space we'd use
> on the hash table too.
> 

The idea is interesting, but does not fit the problem: AFAIK, it will
not be possible to do multiple declarations of the same symbol, which is
needed whenever we want to declare a cond_call() more than once or to
embed it in an inline function.

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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