Bug 459033
Summary: | [Feat] (Public) Have Xen automatically set parameters for 256g system | ||||||
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Product: | Red Hat Enterprise Linux 5 | Reporter: | Russell Doty <rdoty> | ||||
Component: | kernel-xen | Assignee: | Xen Maintainance List <xen-maint> | ||||
Status: | CLOSED CURRENTRELEASE | QA Contact: | Martin Jenner <mjenner> | ||||
Severity: | high | Docs Contact: | |||||
Priority: | high | ||||||
Version: | 5.2 | CC: | adaora.onyia, clalance, micah.parrish, rick.hester, sandy.garza | ||||
Target Milestone: | rc | ||||||
Target Release: | --- | ||||||
Hardware: | All | ||||||
OS: | Linux | ||||||
Whiteboard: | |||||||
Fixed In Version: | Doc Type: | Bug Fix | |||||
Doc Text: | Story Points: | --- | |||||
Clone Of: | Environment: | ||||||
Last Closed: | 2009-01-28 13:30:12 UTC | Type: | --- | ||||
Regression: | --- | Mount Type: | --- | ||||
Documentation: | --- | CRM: | |||||
Verified Versions: | Category: | --- | |||||
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
Cloudforms Team: | --- | Target Upstream Version: | |||||
Embargoed: | |||||||
Bug Depends On: | |||||||
Bug Blocks: | 448753 | ||||||
Attachments: |
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Description
Russell Doty
2008-08-13 20:19:10 UTC
I have made a test RPM available at http://people.redhat.com/riel/.bz453467/ This RPM contains one upstream patch to automatically size the xenheap right (our code base does not have that upstream patch yet) and one to automatically limit the size of dom0 to 32GB - a size big enough that 99% of the users will never notice, yet it should be small enough for the really large systems. Please let me know how the test RPM works for you. Created attachment 315042 [details]
meminfo after applying patch
HP found that the kernel boots but the OS only sees 32Gb of memory. See attached meminfo.
We ran this on a system with 256Gb of memory. (In reply to comment #2) > Created an attachment (id=315042) [details] > meminfo after applying patch > HP found that the kernel boots but the OS only sees 32Gb of memory. See > attached meminfo. Yes, this was done intentionally. Having all 256Gb assigned to the dom0 is generally wasteful in a Xen environment; you'll be eating up a lot of the memory available to dom0 with structures tracking all 256G, when in reality you probably want to give almost all of that memory to your guests. For that reason, we are now restricting the dom0 to 32G. That being said, the machine *overall* should still see 256G of memory; you can confirm this by running "xm info" and looking at the total memory column. If you really feel that you need 256G available to the dom0, you can override the default by passing "dom0_mem=256G" on the hypervisor command-line. Chris Lalancette I tested this patch on the Proliant DL785 with 256GB and it worked. I plan to test it on a DL785 with 512GB. I've been informed that this is an architecture independent problem and that testing with other archs (like the IA64 systems I have) is desired. Would it be possible to build an IA64 kernel with the patch as well? Currently, there appears to be just an x86_64 kernel. What is the desired configuration that this should be tested on? We have a systems with memory configs up to 2TB, but some of those are not immediately available. So, it would help in the resource scheduling to know what the requirement is. Is the test requested to just install and boot with defaults? Or should I set the dom0 memory to be the same as the physical memory (less maybe some amount for the hypervisor)? thanks Rick Hester Well, the patch here won't have any effect on ia64; it's only patching x86. I think we already have similar constraints in place for ia64 (something like 4GB for dom0), but I really don't know any of the details of that arch. If you have the time, it's always good to get testing on ia64 on the largest box you can; but nothing should be different about the linked kernel here with respect to it. Chris Lalancette Marking modified as the private bug that this one is a duplicate of has been integrated into a build: in kernel-2.6.18-107.el5 You can download this test kernel from http://people.redhat.com/dzickus/el5 Please test on your platform. We have tried this kernel out on an IA64 system. We have installed this the 2.6.18-107 kernel on an IA64 system with 64 cpu threads and 512GB of memory. That kernel successfully booted. But then so did the kernel in RHEL 5.2 GA. We then attempted to install and boot on a 128 cpu thread, 1TB IA64 system. Both the 2.6.18-107 and the RHEL 5.2 GA kernels failed to boot. Failure was a hand during boot. This was already known and reported behavior for the RHEL 5.2 GA kernel. So these changes appear to have had no impact on the IA64 kernel (as was expected from previous Red Hat comments). I tested the RHEL5.3 Alpha version of this on a 256GB x86_64 system. Passing dom0_mem=256G on the kernel command line resulted in the same "Xen is relinquishing VGA console" message. dom0_mem=128G booted fine, as did the same kernel without any extra options. Works for me. Keeping in sync with private bz. The fix for this was shipped with RHEL 5.3. |