On Sat, Apr 2, 2022 at 11:36 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> On Sat, Apr 02, 2022 at 03:57:01PM +0800, Hao Lee wrote:
> > Hello,
> >
> > I'm confused about Figure 4.2 and the formula (4.1).
> >
> > Anyone can clarify the confusion? Thanks.
> >
> > On page 56, the book says:
> >
> > 1. LN is the number of lock acquisitions by N threads.
> >
> > Question: Does this mean LN = sum of all the readcounts[i] ?
>
> Yes.
>
> > 2. L1 is the number of lock acquisitions by a single thread
> >
> > Question: which thread is L1 corresponding to? Is "a single thread"
> > selected randomly?
>
> No, L_1 corresponds to the number of acquisitions of a single thread
> in a run where only that one thread was running.
Very clear explanation! Thanks!
>
> And now that you mention it, the text does not make that at all clear,
> so please accept my apologies for the unclarity.
>
> Does the change below help?
>
> The resulting text is:
>
> where N is the number of threads in the current run, L_N is
> the total number of lock acquisitions by all N threads in the
> current run, and L_1 is the number of lock acquisitions in a
> single-threaded run.
Yes. This paragraph is more accurate than before.
Thanks,
Hao Lee
>
> Where the LaTeX "_" subscript operator is used in place of real
> subscripts.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 432a94b0b7e1436a00587a0988fb678def465882
> Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Date: Sat Apr 2 08:30:43 2022 -0700
>
> toolsoftrade: Clarify rwlock efficiency formula description
>
> Reported-by: Hao Lee <haolee.swjtu@xxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> diff --git a/toolsoftrade/toolsoftrade.tex b/toolsoftrade/toolsoftrade.tex
> index 833ec697..d6662f8c 100644
> --- a/toolsoftrade/toolsoftrade.tex
> +++ b/toolsoftrade/toolsoftrade.tex
> @@ -890,9 +890,10 @@ The actual value plotted is:
> \begin{equation}
> \frac{L_N}{N L_1}
> \end{equation}
> -where $N$ is the number of threads,
> -$L_N$ is the number of lock acquisitions by $N$ threads, and
> -$L_1$ is the number of lock acquisitions by a single thread.
> +where $N$ is the number of threads in the current run,
> +$L_N$ is the total number of lock acquisitions by all $N$ threads in the
> +current run, and
> +$L_1$ is the number of lock acquisitions in a single-threaded run.
> Given ideal hardware and software scalability, this value will always
> be 1.0.
>
