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From: Akira Yokosawa <akiyks@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: perfbook@vger.kernel.org, Akira Yokosawa <akiyks@gmail.com>
Subject: [Possible BUG] count_lim_atomic.c fails on POWER8
Date: Sun, 21 Oct 2018 00:53:17 +0900	[thread overview]
Message-ID: <d6abdc9c-9d0e-9435-05be-85a4fe9d3347@gmail.com> (raw)

Hi Paul,

I just noticed occasional error of count_lim_atomic.c on POWER8 at current master.
As I've recently touched the code under Codesamples/count/, I also tested on
the tag "v2017.11.22a", and saw the same behavior.

The POWER8 virtual machine is Ubuntu 16.04.

Example output:

$ ./count_lim_atomic 6 uperf 1
!!! Count mismatch: 0 counted vs. 8 final value
n_reads: 0  n_updates: 26038000  nreaders: 0  nupdaters: 6 duration: 240
ns/read: nan  ns/update: 55.3038

$ ./count_lim_atomic 6 perf 1
!!! Count mismatch: 0 counted vs. 11 final value
n_reads: 287000  n_updates: 1702000  nreaders: 6  nupdaters: 1 duration: 240
ns/read: 5017.42  ns/update: 141.011

As you see, the final count check of zero fails even when nupdaters == 1.

I have no idea what's wrong in count_lim_atomic.c.

Can you look into this? There might be something wrong in the header file
under CodeSamples/arch-ppc64.h.

On x86_64, I've never seen the count mismatch.

         Thanks, Akira
 


             reply	other threads:[~2018-10-20 15:53 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-20 15:53 Akira Yokosawa [this message]
2018-10-20 16:36 ` [Possible BUG] count_lim_atomic.c fails on POWER8 Paul E. McKenney
2018-10-24 15:53   ` Junchang Wang
2018-10-24 22:05     ` Akira Yokosawa
2018-10-24 22:29       ` Akira Yokosawa
2018-10-25  2:18         ` Junchang Wang
2018-10-25  2:11       ` Junchang Wang
2018-10-25  9:45         ` Paul E. McKenney
2018-10-25 12:23           ` Akira Yokosawa
2018-10-25 14:09           ` Junchang Wang
2018-10-25 15:17             ` Akira Yokosawa
2018-10-25 22:04               ` Akira Yokosawa
2018-10-26  0:58                 ` Junchang Wang
2018-10-27 14:56                   ` Akira Yokosawa
     [not found]                     ` <20181028001723.GJ4170@linux.ibm.com>
2018-10-28 12:08                       ` Junchang Wang
2018-10-28 13:19                         ` Paul E. McKenney
2018-10-28 13:22                         ` Akira Yokosawa
2018-10-28 14:24                       ` Akira Yokosawa
2018-10-28 16:43                         ` Paul E. McKenney
2018-10-29 14:45                           ` Akira Yokosawa
2018-10-29 15:30                             ` Paul E. McKenney
2018-10-26  1:12                 ` Akira Yokosawa
2018-10-26 11:34                   ` Akira Yokosawa
2018-10-26 16:06                     ` Junchang Wang
2018-10-25 15:24             ` Paul E. McKenney

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