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From: Alan Huang <mmpgouride@gmail.com>
To: perfbook@vger.kernel.org
Subject: Question: What does "one thread can enter but two threads can exit" mean?
Date: Tue, 11 Apr 2023 00:40:19 +0800	[thread overview]
Message-ID: <FE0E33DE-C0A0-4065-99CC-5F0AB58E7A67@gmail.com> (raw)

Hi,

I am reading section 6.5.4, there is one paragraph said:

> The fraction of cells visited by PWQ is similar to that of SEQ. In addition, PWQ’s solution time is greater than that of PART, even for equal visit fractions. The reason for this is shown in Figure 6.28, which has a red circle on
> Figure 6.29: Effect of Compiler Optimization (-O3)
> each cell with more than two neighbors. Each such cell can result in contention in PWQ, because one thread can enter but two threads can exit, which hurts performance,

I don't know why there is competition only when a cell has more than two neighbors?

And as the subject said, what does "one thread can enter but two threads can exit” mean?

After checking the code(maze_fg.c), Doesn’t every cell in the maze can result in contention?

Thanks,
Alan

next             reply	other threads:[~2023-04-10 16:40 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-10 16:40 Alan Huang [this message]
2023-04-10 18:14 ` Question: What does "one thread can enter but two threads can exit" mean? Paul E. McKenney

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