Date: Fri, 11 Jun 1999 09:59:25 -0500 From: Chris Costello <chris@calldei.com> To: "David E. Cross" <crossd@cs.rpi.edu> Cc: freebsd-hackers@FreeBSD.ORG, freebsd-smp@FreeBSD.ORG Subject: Re: High syscall overhead? Message-ID: <19990611095925.V57174@holly.dyndns.org> In-Reply-To: <199906111440.KAA70517@cs.rpi.edu>; from David E. Cross on Fri, Jun 11, 1999 at 10:40:37AM -0400 References: <199906111440.KAA70517@cs.rpi.edu>
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On Fri, Jun 11, 1999, David E. Cross wrote:
> Just doing some performance testing and I noticed something rather
> disturbing....
>
> Here is the test program:
> int main (void)
> {
> int count=0;
> for(count=0;count <10000000;++count)
> getppid();
>
> return 0;
> }
>
> The time on linux for this program is ~5 seconds (linux "time" reports 3.x, but
> a wall clock clearly shows 5.x, go fig). FreeBSD reports 18.x seconds?!. I
> have a dual processor system and decided to parallel run them... it took
> 52!?! seconds, linux on the same was again about 5. Looking through the
> exception.s it appears that on entry to the kernel an MP lock is obtained...
> I thought we had splX(); to protect concurancy in the kernel.
('sc' being the program above, compiled without optimization,
just with cc -o sc sc.c)
$ time ./sc
10.04s real 3.89s user 5.64s system
I counted between around 9 and a half to 10 and a half seconds
on my wall clock (trusty old GE, same model they have in public
schools).
Copyright (c) 1992-1999 The FreeBSD Project.
Copyright (c) 1982, 1986, 1989, 1991, 1993
The Regents of the University of California. All rights reserved.
FreeBSD 4.0-CURRENT #4: Sun May 30 04:22:23 CDT 1999
root@holly.dyndns.org:/usr/src/sys/compile/Holly
Timecounter "i8254" frequency 1193182 Hz
CPU: AMD-K6(tm) 3D processor (350.80-MHz 586-class CPU)
Origin = "AuthenticAMD" Id = 0x580 Stepping=0
Features=0x8001bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,MMX>
real memory = 67108864 (65536K bytes)
sio0: system console
avail memory = 62267392 (60808K bytes)
SMP specific bug, perhaps?
>
> I am just curious what's the story with this. On some of my other tests it is
> clear that FreeBSD is handling concurancy much better than linux (by an equal
> factor actually, and on "real" tasks like real I/O handling).
>
> --
> David Cross | email: crossd@cs.rpi.edu
> Systems Administrator/Research Programmer | Web: http://www.cs.rpi.edu/~crossd
> Rensselaer Polytechnic Institute, | Ph: 518.276.2860
> Department of Computer Science | Fax: 518.276.4033
> I speak only for myself. | WinNT:Linux::Linux:FreeBSD
>
>
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--
Chris Costello <chris@calldei.com>
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