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Re: [Xen-devel] [Patch] support of lock profiling in Xen

To: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [Patch] support of lock profiling in Xen
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 08 Oct 2009 09:38:09 +0100
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On 08/10/2009 09:27, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:

>> If lock profiling is compiled in, have a static array of lock-profile
>> descriptors (keeps things simple - could make it a growable array, or
>> something). On lock init, walk the array looking for that name. If found,
>> write the entry index into a new field in the spinlock struct. If not found,
>> allocate next entry in lock-profile array, init it, and write its index into
>> the spinlock struct.
> 
> Don't you think a solution like for performance counters would be better then?
> The index would be in a header file and the sums could be held per-cpu to
> avoid races.
> It would even be possible to define lock arrays if summing up all data for
> e.g. domain specific locks is not desired.

It's just a question of impact on our existing locking API. I'd like to
minimise that. I'm not particularly a fan of the perfc stuff.

 -- Keir



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