z/VM doesn't have a short cut to determine that no pages have changed. So for a guest over 100GB, it has to examine over 26 million things multiple times. Validating the I/O is drained is another aspect, but my guess is the traversing of the DAT structures is the biggest factor.
Regards, Bill ___________________________________________________________________________________________ Bill Bitner - z/VM Client Focus and Care - 607-429-3286 bitn...@us.ibm.com "Making systems practical and profitable for customers through virtualization and its exploitation." - z/VM From: Grzegorz Powiedziuk <gpowiedz...@gmail.com> To: LINUX-390@VM.MARIST.EDU Date: 08/17/2020 11:51 PM Subject: [EXTERNAL] Re: vmrelocate and quiescence time Sent by: Linux on 390 Port <LINUX-390@VM.MARIST.EDU> On Mon, Aug 17, 2020 at 12:26 PM Bill Bitner <bitn...@us.ibm.com> wrote: > I take a few days off and a fun topic comes up that I mostly miss. :-) > > We did a Live Virtual Class on this back when SSI first came out. A few > things have changed, but you may find value in it: > http://www.vm.ibm.com/education/lvc/zvmlvc.html > The charts for the presentation are > http://www.vm.ibm.com/education/lvc/LVC0227.pdf > > This is great! Thank you. Although this brings a few more questions, it was definitely very helpful. - chart on page 24 idle case (0GB change) had a quiesce time 8s - I wonder why. That VM in this test was probably >100GB so more or less close to my case. But I thought that if there are close to 0 changes, then the last pass should be just a "formality"? I was relocating my VM with DB2 being stopped! There were just few idle processes left and yet it took 20-30s of freeze time. Of course I am doing sync and not immediate. Seems like I should be below <10s even with just 2CTCs (although I am hoping to get 2 more) by looking at these charts. - document says that I/O device count matters as well. We have 4 FCP channels with quite a big number of luns (>20), would that make a big difference? I will look into anything related in perfsvm thanks again. Gregory ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www2.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www2.marist.edu/htbin/wlvindex?LINUX-390
