As always, it depends. However my guess is that it should help machine
performance. Without PPF, when a page fault occurs the whole virtual
machine is suspended until the page is made available. With PPF the page
fault is reflected to the virtual machine and the machine continues to run.
The virtual machine must decide what task was running, suspend it, run
other taks, and then when notified that the page is available to reschedule
the suspended task. There is some task switching overhead involved but al
least the virtual machine can still keep running.
To: [EMAIL PROTECTED]
"Scully, William cc: (bcc: Michael Short/Towers
Perrin)
P" Subject: SLES 8 and Pseudo Page Faults
<[EMAIL PROTECTED]
a.com>
Sent by: Linux on
390 Port
<[EMAIL PROTECTED]
IST.EDU>
07/16/2003 02:48
PM
Please respond to
Linux on 390 Port
I see (via "make xconfig") in SLES8 that Pseudo Page Fault support is
enabled. The associated help says that if the PFAULT macro cannot be used
then PAGEEX (sic) will be used. However, to use PFAULT the virtual machine
must be in XC-mode operation, according to the IBM CP Programming Services
manual. The SLES8 install doc shows a sample directory entry with MACHINE
ESA specified. Also, when I issue a CP QUERY SET it shows that PAGEX is
OFF. I gather from these facts that Pseudo Page Fault support must not be
actually in use. Some questions:
- Should we be running with MACHINE XC specified in the directory entry for
the SLES8 servers?
- If not running MACHINE XC, should I be specifying SET PAGEX ON before
booting SLES8?
- Finally, and more generally, should I even bother? That is, will Pseudo
Page Fault support make running SLES8 faster?
Thanks for any insight that you may have on this topic.
William P. Scully
Systems Programmer
Computer Associates International, Inc
2291 Wood Oak Drive
Unit 5-29C
Herndon, Virginia 20171
[EMAIL PROTECTED]
