> One of the most visible things is disk I/O where CP needs to > put the guest data pages under the bar and Linux decides to > use different pages for I/O all the time. The recent > distributions have options in the to prevent that from happening.
True for ECKD, but nor for SCSI - though this z/VM restriction hits both. Anyway, the way to go is z/VM 5.2 which doesn't come with this issue. Mit freundlichen Grüßen / with kind regards Martin Peschke IBM Deutschland Entwicklung GmbH Linux for zSeries Development Phone: +49-(0)7031-16-2349 Rob van der Heij <[EMAIL PROTECTED]> Sent by: Linux on 390 Port <[email protected]> 06/10/2005 17:30 Please respond to Linux on 390 Port To: [email protected] cc: Subject: Re: paging of 64-bit hosts v 31-bit hosts under VM On 10/6/05, John P Taylor <[EMAIL PROTECTED]> wrote: > I understand that all 31-bit hosts must utilise storage below the 2G > line, and consequently if you have many active hosts and you over commit > storage, your VM system will page, even if the sum of the working sets > of all hosts is say 50% (or less) . What I'm not so sure about, is > whether equivalently sized 64-bit hosts will page less, any ideas? You're mistaken. The bitness of the guest has nothing to do with that. The issue is in the bitness of some code paths in CP that require the page to move under the bar to do things with the data inside. Running the guest in 64-bit will not help you anything (but 64-bit guests have an excuse for bigger virtual machines and thus make it worse). One of the most visible things is disk I/O where CP needs to put the guest data pages under the bar and Linux decides to use different pages for I/O all the time. The recent distributions have options in the to prevent that from happening. Rob -- Rob van der Heij rvdheij @ gmail.com ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
