On Wed, Jul 14, 2010 at 06:29:14PM -0500, Nicolas Williams wrote:
> On Thu, Jul 15, 2010 at 01:27:06AM +0200, ????? ???????????? wrote:
> > A fairly simple - but not perfectly accurate - test case would be to
> > run ksh93 on Linux and Solaris and let it call /bin/true in a loop.
> >
> > The numbers which follow are for identical ksh93 versions built with
> > the same gcc version and /bin/true a simple main() { return 0 ;}:
> >
> > 1. Timing values for Solaris B134 on bare metal hardware:
> > time ksh -c 'integer i ; for (( i=0 ; i < 100000 ; i++ )) ; do /bin/true ;
> > done'
> >
> > real 9m29.75s
> > user 0m8.55s
> > sys 2m46.89s
The real time number here doesn't look right. In particular, you're
only using < 3m of CPU time, but you're spending almost 9.5m wall time
to complete the operation.
When I run this command on my system, I get the following timing data:
real 53.750666106
user 14.188122722
sys 30.753105797
This still isn't as fast as Linux, but it's not 9 minutes.
When I trussed this, I got the following output:
syscall seconds calls errors
_exit .000 100001
read .000 1
open .833 200009 100002
close .229 100007
time .000 1
brk .000 8
stat .000 12 3
lseek .000 1
getpid .291 200004
getuid .000 2
fstat .000 8
access .000 1
getsid .153 100000
getgid .000 2
sysi86 .169 100001
ioctl .407 200004
execve 8.471 100002
umask .000 2
fcntl .000 1
readlink .000 1
sigprocmask .145 100000
sigaction .187 100003
sigfillset .000 1
getcontext .213 100002
setcontext .221 99999
setustack 2.645 100002
waitid 1.171 399786 299786
mmap 1.823 600017
mmapobj 1.843 100006
getrlimit .176 100002
memcntl .932 300011 1
sysconfig .142 100008
sysinfo .165 100003
vforkx 1.531 100000
yield .000 1
lwp_sigmask .934 600001
lwp_private .148 100002
schedctl .147 100001
resolvepath 1.606 300010
stat64 .763 200002
-------- ------ ----
sys totals: 25.359 4699925 399792
usr time: 16.526
elapsed: 222.140
Keep in mind that the timing from truss has a lot of probe effect, so
don't consider these numbers the actual speed. However, the system call
that's using the most time here is execve, not vfork. The wall time is
still much higher than the CPU time, so I would investigate where this
process is waiting.
A couple of possibilities:
1. The swap reservations are done differently on Linux than Solaris. It
might be the case that you're running out of memory, or waiting for swap
to become available.
2. Perhaps ksh is waiting for the wrong thing to complete here?
I would dtrace for what's causing your processes to go off CPU and
aggregate for those stacks that are consuming the most time waiting.
HTH,
-j
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