Date: Sat, 20 Dec 2003 00:24:29 +1100 From: Tim Robbins <tjr@freebsd.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern sysv_sem.c Message-ID: <20031219132429.GA913@wombat.robbins.dropbear.id.au> In-Reply-To: <200312191307.hBJD7HYo099172@repoman.freebsd.org> References: <200312191307.hBJD7HYo099172@repoman.freebsd.org>
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On Fri, Dec 19, 2003 at 05:07:17AM -0800, Tim J. Robbins wrote:
> tjr 2003/12/19 05:07:17 PST
>
> FreeBSD src repository
>
> Modified files:
> sys/kern sysv_sem.c
> Log:
> Reduce the overhead of semop() by using the kernel stack instead of
> malloc'd memory to store the operations array if it is small enough
> to fit.
FWIW, wall time for 100,000 increment/decrement pairs on a single semaphore:
x before
+ after
+--------------------------------------------------------------------------+
| ++ + xxx |
|+++++ + xxx x|
| |A_| |A_| |
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 9 5.35 5.5 5.39 5.3933333 0.044440972
+ 9 3.8 3.93 3.85 3.8566667 0.041231056
Difference at 95.0% confidence
-1.53667 +/- 0.0428394
-28.492% +/- 0.794303%
(Student's t, pooled s = 0.0428661)
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