spending lots of time in spin locks

Brad Guillory · *nix forums beginner Joined: 03 Feb 2005 Posts: 3

If I should go elsewhere I apologize in advance; please just point me
in the right direction. I also posted to comp.unix.sco.programmer, but
that group appears dead.

There exists a SCO box (please keep reading):
# uname -X

System = SCO_SV
Node = *HIDDEN*
Release = 3.2v5.0.6
KernelID = 2000-07-27
Machine = Xeon
BusType = ISA
Serial = *HIDDEN*
Users = 255-user
OEM# = 0
Origin# = 1
NumCPU = 1

It runs a single curses based application (that my company maintains)
for about 250 users. After upgrading the application this weekend the
average "load" during peak hours jumped from 1.2 to 15+ (yes more than
10 fold).

I went through the sar -A report and found the following differences
between Friday (before the upgrade) and Tuesday (after the upgrade):

(forgive me if this is too verbose)

00:00:00 scall/s sread/s swrit/s fork/s exec/s rchar/s wchar/s
(-c)
FRI 10:00:00 58500 5777 2442 1305.29 11.28 1243788 35388
TUE 10:00:00 275583 3405 540 13.51 12.07 1641830 33363

As you can see the scall/s is much higher, but the characters read per
call to read is is higher (better) same for the writes. I figure that
this may be caused by longer times between calls to read() and write().
I am trying to account for the spike in scall/s.

scall/s
total number of system calls per second

sread/s
number of read(S) calls per second

swrit/s
number of write(S) calls per second

fork/s number of fork(S) calls per second

exec/s number of exec(S) calls per second

rchar/s
number of characters read per second (by read)

wchar/s
number of characters written per second (by write)

00:00:00 vflt/s pflt/s pgfil/s rclm/s (-p)
FRI 10:00:00 4070.80 19542.89 0.00 0.00
TUE 10:00:00 114.18 387.32 0.03 0.00

This seems interesting but I have no idea what would cause it.

vflt/s address translation page faults (valid page not in
memory)
per second

pflt/s page faults per second caused by attempts to write to
a page
marked ``copy-on-write'' (COW), or by protection
errors
(illegal access to page)

pgfil/s
address translation faults per second satisfied by
paging in
from filesystem

rclm/s pages added to the free list per second

I relinked the kernel and enabled prfld (the system profiler) to obtain
the following stats:

spltty 30.00
splx 35.16
sys_call 5.73
user 14.18

Can anyone point me to the next step? How can I find what library
calls in turn call spltty?

TIA, Brad Guillory

Guest

How fast CPU do you have ?

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