linux-kernel - RE: [PATCH v3 1/2] lib/test_bitops: Add benchmark test for fns()

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Date: Sun, 5 May 2024 13:03:23 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Kuan-Wei Chiu' <visitorckw@...il.com>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "yury.norov@...il.com" <yury.norov@...il.com>
CC: "linux@...musvillemoes.dk" <linux@...musvillemoes.dk>,
	"n26122115@...ncku.edu.tw" <n26122115@...ncku.edu.tw>,
	"jserv@...s.ncku.edu.tw" <jserv@...s.ncku.edu.tw>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] lib/test_bitops: Add benchmark test for fns()

From: Kuan-Wei Chiu
> Sent: 01 May 2024 08:17
> 
> Introduce a benchmark test for the fns(). It measures the total time
> taken by fns() to process 1,000,000 test data generated using
> get_random_long() for each n in the range [0, BITS_PER_LONG).
> 
> example:
> test_bitops: fns:          5876762553 ns, 64000000 iterations

Great benchmark....

The compiler almost certainly optimises it all away.

Assigning the result of fns() to a file scope (global) volatile int
should stop that happening.

And a real test would actually check the result - just in case
someone does something silly.

	David

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