Re: enhanced DAT facility
On Fri, 30 Oct 2009 15:33:09 -0400 Alan Altmark said:
>On Friday, 10/30/2009 at 05:14 EDT, "DUBOIS Laurent (EXT DUBOIS)"
> wrote:
>
>> I have a zTPF guy who tells me that z/TPF will support the enhanced DAT
>>
>> facility soon to improve performance.
>> When I checked our CPU facility list
>> installed, the machine native shows
>> the enhanced DAT facility installed, but
>> z/VM does not.
>>
>> I am wondering if this facility is z/VM generation option.
>>
>> Have anybody an idea ?
>
>No, you cannot persuade z/VM to use enhanced DAT ("EDAT").
>
>Another religious war in the offing. One of the ways EDAT improves
>performance is by eliminating page tables (leaving more room in the cache
>for Good Things) and speeding up the address translation process. All
>"pages" are 1MB (the size of a segment). When paging, that means you have
>to swap 256 4K pages at once, and they have to be contiguous in real
>memory. So while you get some good benefits, memory fragmentation can
>create significant pain.
>
>And in a virtual environment, what if the guest isn't using EDAT? You
>could end up with both 1M and 4K pages in the system, creating the need
>for *more* memory management.Intellectually, the best result
>will be when the hypervisor and the virtual machines both use 1M pages.
>
>We have it on our to-do list, but it isn't a trivial piece of work. I
>just disassembled/reassembled my wife's laptop, so the imagery is fresh:
>The concept of a 4K page is part of the CP backplane and
>zero-insertion-force sockets were not used. ("Who would ever want a page
>> 4K?") It's soldered tight, as it were, so disengaging the rest of CP
>from that infrastructure without damaging delicate components will be
>challenging.:-)It's a good thing we thrive on such challenges!!
So are you saying it's just like a Mac?
/ahw
>
>Alan Altmark
>z/VM Development
>IBM Endicott
Re: enhanced DAT facility
On Fri, Oct 30, 2009 at 10:37 PM, Schuh, Richard wrote: > Chuckie must be in a good mood if he allowed you to give a one-word reply, > especially on a Friday. He's busy for Halloween http://www.youtube.com/watch?v=mH2rd0wPG9A
Re: enhanced DAT facility
Chuckie must be in a good mood if he allowed you to give a one-word reply, especially on a Friday. Regards, Richard Schuh > -Original Message- > From: The IBM z/VM Operating System > [mailto:ib...@listserv.uark.edu] On Behalf Of Alan Altmark > Sent: Friday, October 30, 2009 2:34 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: enhanced DAT facility > > On Friday, 10/30/2009 at 03:37 EDT, Neale Ferguson > > wrote: > > Can guests use it under z/VM? > > No. > > Alan Altmark > z/VM Development > IBM Endicott >
Re: enhanced DAT facility
On Friday, 10/30/2009 at 03:37 EDT, Neale Ferguson wrote: > Can guests use it under z/VM? No. Alan Altmark z/VM Development IBM Endicott
Re: enhanced DAT facility
No, neither guest support nor host exploitation is included in current
versions of z/VM.
- Bill Holder, z/VM Development, IBM
On Fri, 30 Oct 2009 15:36:52 -0400, Neale Ferguson
wrote:
>Can guests use it under z/VM?
>
>
>On 10/30/09 3:33 PM, "Alan Altmark" wrote:
>
>> No, you cannot persuade z/VM to use enhanced DAT ("EDAT").
>>
>> Another religious war in the offing. One of the ways EDAT improves
>> performance is by eliminating page tables (leaving more room in the ca
che
>> for Good Things) and speeding up the address translation process. All
>> "pages" are 1MB (the size of a segment). When paging, that means you
have
>> to swap 256 4K pages at once, and they have to be contiguous in real
>> memory. So while you get some good benefits, memory fragmentation can
>> create significant pain.
Re: enhanced DAT facility
Can guests use it under z/VM?
On 10/30/09 3:33 PM, "Alan Altmark" wrote:
> No, you cannot persuade z/VM to use enhanced DAT ("EDAT").
>
> Another religious war in the offing. One of the ways EDAT improves
> performance is by eliminating page tables (leaving more room in the cache
> for Good Things) and speeding up the address translation process. All
> "pages" are 1MB (the size of a segment). When paging, that means you have
> to swap 256 4K pages at once, and they have to be contiguous in real
> memory. So while you get some good benefits, memory fragmentation can
> create significant pain.
Re: enhanced DAT facility
On Friday, 10/30/2009 at 05:14 EDT, "DUBOIS Laurent (EXT DUBOIS)"
wrote:
> I have a zTPF guy who tells me that z/TPF will support the enhanced DAT
>
> facility soon to improve performance.
> When I checked our CPU facility list
> installed, the machine native shows
> the enhanced DAT facility installed, but
> z/VM does not.
>
> I am wondering if this facility is z/VM generation option.
>
> Have anybody an idea ?
No, you cannot persuade z/VM to use enhanced DAT ("EDAT").
Another religious war in the offing. One of the ways EDAT improves
performance is by eliminating page tables (leaving more room in the cache
for Good Things) and speeding up the address translation process. All
"pages" are 1MB (the size of a segment). When paging, that means you have
to swap 256 4K pages at once, and they have to be contiguous in real
memory. So while you get some good benefits, memory fragmentation can
create significant pain.
And in a virtual environment, what if the guest isn't using EDAT? You
could end up with both 1M and 4K pages in the system, creating the need
for *more* memory management.Intellectually, the best result
will be when the hypervisor and the virtual machines both use 1M pages.
We have it on our to-do list, but it isn't a trivial piece of work. I
just disassembled/reassembled my wife's laptop, so the imagery is fresh:
The concept of a 4K page is part of the CP backplane and
zero-insertion-force sockets were not used. ("Who would ever want a page
> 4K?") It's soldered tight, as it were, so disengaging the rest of CP
from that infrastructure without damaging delicate components will be
challenging.:-)It's a good thing we thrive on such challenges!!
Alan Altmark
z/VM Development
IBM Endicott
Re: enhanced DAT facility
z/VM does not currently support the Enhanced DAT Facility. And it's not quite as simple as "improves performance". There are tradeoffs involved, and it's not exactly a small undertaking. - Bill Holder, z/VM Development, IBM > Hi, > > I have a zTPF guy who tells me that z/TPF will support the enhanced DAT > facility soon to improve performance. > When I checked our CPU facility list installed, the machine native show s > the enhanced DAT facility installed, but z/VM does not. > > I am wondering if this facility is z/VM generation option. > > Have anybody an idea ? > > Regards > > :-) Laurent Dubois - Equipe VM
enhanced DAT facility
Hi, I have a zTPF guy who tells me that z/TPF will support the enhanced DAT facility soon to improve performance. When I checked our CPU facility list installed, the machine native shows the enhanced DAT facility installed, but z/VM does not. I am wondering if this facility is z/VM generation option. Have anybody an idea ? Regards :-) Laurent Dubois - Equipe VM _ Laurent Dubois * laurent.dub...@sncf.fr * 03 28 55 63 88 - 22 53 88 * 03 28 55 63 22 - 22 63 22 SNCF - DSIV XS MM Systeme VM Centre Informatique de Lille Pont de Tournai - 59041 LILLE CEDEX _ --- Ce message et toutes les pièces jointes sont établis à l'intention exclusive de ses destinataires et sont confidentiels. L'intégrité de ce message n'étant pas assurée sur Internet, la SNCF ne peut être tenue responsable des altérations qui pourraient se produire sur son contenu. Toute publication, utilisation, reproduction, ou diffusion, même partielle, non autorisée préalablement par la SNCF, est strictement interdite. Si vous n'êtes pas le destinataire de ce message, merci d'en avertir immédiatement l'expéditeur et de le détruire. --- This message and any attachments are intended solely for the addressees and are confidential. SNCF may not be held responsible for their contents whose accuracy and completeness cannot be guaranteed over the Internet. Unauthorized use, disclosure, distribution, copying, or any part thereof is strictly prohibited. If you are not the intended recipient of this message, please notify the sender immediately and delete it.
