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Date: Sun, 24 Jul 2005 12:12:11 -0700 (PDT)
From: Ciprian <cipicip@yahoo.com>
Subject: kernel 2.6 speed
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi guys!

I got a question for you. Apparently kernel 2.6 is
much slower then 2.4 and about 30 times slower then
the windows one.

I'm not an OS guru, but I ran a little and very simple
test. The program bellow, as you can see, measures the
number of cycles performed in 30 seconds.

//----------------- START CODE --------------------

#include <stdio.h>
#include <time.h>


int main()
{
time_t initialTime;
time_t testTime;
long counter = 0;
double test = 1;


time(&initialTime);
testTime = initialTime;

printf("Here we go...\n");

while((testTime-initialTime) < 30)
{
time(&testTime);
test /= 10;
test *= 10;
test += 10;
test -= 10;

counter ++;

}

printf("No. of cycles: %ld\n", counter);

return 0;
}

//---------------- END CODE -------------------


In windows were performed about 300 millions cycles,
while in Linux about 10 millions. This test was run on
Fedora 4 and Suse 9.2 as Linux machines, and Windows
XP Pro with VS .Net 2003 on the MS side. My CPU is a
P4 @3GHz HT 800MHz bus.

I published my little test on several forums and I
wasn't the only one who got these results. All the
other users using 2.6 kernel obtained similar results
regardless of the CPU they had (Intel or AMD). 

Also I downloaded the latest kernel (2.6.12),
configured it specifically for my machine, disabled
all the modules I don't need and compiled it. The
result was a 1.7 MB kernel on which KDE moves faster,
but the processing speed it's the same - same huge
speed ratios.

Also, it shouldn't have any importance, but my HDD is
SATA so the specific modules were required. I don't
think its SCSI modules have any impact on the
processing speed, but you know more on the kernel
architecture then I do.

Now, can anyone explain this and suggest what other
optimizations I should use? The 2.4 version was a lot
faster. I thought the newer versions were supposed to
work faster (or at least just as fast) AND to offer
extra features.

Any help would appreciate.

Thanks,
Ciprian



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