Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable

From: Steven Rostedt
Date: Wed Jul 27 2005 - 22:46:45 EST

On Wed, 2005-07-27 at 23:32 -0400, Steven Rostedt wrote:
> New benchmarks with my own formula.

Take two: I ran this on my laptop (IBM ThinkPad G41 with an 3.3GHz
Pentium 4 HT processor, yeah yeah, no battery life :-). But this has an
older compiler.

$ gcc -v
Reading specs from /usr/lib/gcc-lib/i486-linux-gnu/3.3.6/specs
Configured with: ../src/configure -v --enable-languages=c,c
++,java,f77,pascal,objc,ada,treelang --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared
--enable-__cxa_atexit --with-system-zlib --enable-nls
--without-included-gettext --enable-clocale=gnu --enable-debug
--enable-java-gc=boehm --enable-java-awt=xlib --enable-objc-gc
Thread model: posix
gcc version 3.3.6 (Debian 1:3.3.6-7)

Here's the results on it:

compiled again with "gcc -O2 -o ffb ffb.c"

/* comments embedded */

sched=128 ffb=160 my=160
/* this is a 3.3GHz so clocks look good */
clock speed = 00000000:c5e54f4c 3320139596 ticks per second
sched=159 ffb=159 my=159
last bit set
generic ffb: 00000000:0a25b1d0
/* Hmm, all generic ffb is even slower? do I blame gcc or Intel? */
time: 0.051275712us
sched ffb: 00000000:0023ae21
/* double Hmm, Ingo's is faster !? */
time: 0.000704289us
my ffb: 00000000:019c458d
/* look at this, mine is the same. Are the three bears coming around soon :-) */
time: 0.008137802us
sched=0 ffb=0 my=0

first bit set
generic ffb: 00000000:09766c3c
time: 0.047816034us
sched ffb: 00000000:0023c79f
time: 0.000706254us
my ffb: 00000000:005a8758
time: 0.001786939us

OK, still looks like the generic ffb can be changed. Unless I'm missing
something, this shows that I probably should be sending in a patch now
to replace the find_first_bit. Ingo's sched_find_first_bit is still the
winner, but that is customed to the scheduler, until we need a
configurable priority.

What do you think?

-- Steve

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