----- Original Message -----
From: "Mark Zelden" <[email protected]>
Newsgroups: bit.listserv.ibm-main
Sent: Saturday, August 14, 2010 10:27 AM
Subject: Re: Anyone Using z10 Large Pages in anger?
On Sat, 14 Aug 2010 10:24:02 +0100, Graham Harris <[email protected]>
wrote:
Is anyone actively using z10 (or z196!!) Large Pages in any significant
way
yet?
Yes. On my clients WebSphere LPARs. First we used a small LFAREA and
migrated some WAS regions to 64-bit. All was fine. Then on a weekend we
allocated about 40G more to LFAREA and IPLed with the plan of converting
more regions during the week. Much to our chagrin, Monday morning
was a nightmare because paging went through the roof and thousands
of enclaves were backed up in the system and couldn't be processed.
It turns out the support didn't work as documented and 1M pages weren't
really used for 4K when there was a shortage! After we opened a Sev 1
PMR with IBM during the problem IBM said something like "well, this isn't
really supported".
Huh?!!! This was z/OS 1.10 and I thought the support was z/OS 1.9
with PTFs. :-) The SHARE presentations I was at and documentation I
had
read sure made it sound like it was supported!
During a tech call with IBM they admitted that the support wasn't working
as intended (?) and the LFAREA was really just "stuck" there all for 1M
pages and couldn't be used to back 4K page requests. So in essence we
lost 40G of real memory when we IPLed.
We converted a some additional regions to 64-bit over a few hours around
lunch
time to limp through the day without an outage, then backed out the
changes
that evening with an IPL along with any WAS regions that were converted
to 64-bit.
We are still using large pages but have been doing it in steps over the
last
6 months (IPL with larger LFAREA, convert more WAS regions to 64-bit).
We are z/OS 1.11 now and I honestly can't say if anything was changed in
the code or if it works yet. The person closest to this works on the
WebSphere team and I haven't asked. Maybe Elpida is lurking and
can say.
This weekend my client is doing a memory upgrade and also increasing
LFAREA
in one of the LPARs from around 64G to 80G (out of about 170G total).
Wow. Hard to believe Elpida would have shipped that crap. Thanks for the
heads up on Large Page non-support.
Regards,
Tom Conley
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