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Date: Sat, 25 Jun 2022 08:57:35 +0900
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 <20220624233316.GF1790663@paulmck-ThinkPad-P17-Gen-1>
From: Akira Yokosawa <akiyks@gmail.com>
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To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: perfbook@vger.kernel.org, Akira Yokosawa <akiyks@gmail.com>
List-ID: <perfbook.vger.kernel.org>

On Fri, 24 Jun 2022 16:33:16 -0700, Paul E. McKenney wrote:
> On Sat, Jun 25, 2022 at 08:12:09AM +0900, Akira Yokosawa wrote:
>> Hi Paul,
>>
>> I find the analogy of Figure 7.11 hard to grasp.
>>
>> Whether a lock is global or per-instance, the cost of locking
>> (saw kerf) is observed only when a CPU/thread does the locking
>> operation.
>>
>> In this figure, does each board represent data elements, not a
>> CPU/thread?  If this is the case, what does the waste of "saw kerf"
>> mean?
>>
>> What am I missing?
>>
>> (I hope I am clear enough on what I don't get...)
> 
> It might well be that I am getting too excited about this one.  ;-)
> 
> Maybe I need to drop it.  At the very least, I need to much more clearly
> explain it.
> 
> But...
> 
> Each board represents one lock.  The "saw kerf" is the time lost when
> releasing that lock and someone else immediately acquiring it.
> 
> Does that help?

Well then, why does the left side figure have ten boards?

        Thanks, Akira

> 
> 							Thanx, Paul