XCP-ng 8.0.0 Beta now available!
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@peder Thanks for testing. It confirms our recent findings related to PV guests indeed! We're working on it and will post here once it's fixed.
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@stormi Nice to hear, thanks!
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@peder Fixed! This fix will be available (as soon as possible) in a future xcp-emu-manager package.
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I have updated https://github.com/xcp-ng/xcp/wiki/Test-XCP with lots of new tests for those who need ideas
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Just FYI - I have performed CPU and PGBench benchmarks on XCP-ng 8 beta 1, both with Hyperthreading enabled and disabled when running two identical VMs under different types of low, medium and heavy CPU load.
Results are available here: https://github.com/sammcj/benchmark_results/tree/master/xcpng/8/hyperthreading_impact
TLDR;
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Significant performance decrease (38.7725%) when running multithreaded Sysbench CPU benchmarks in parallel on two VMs when hyperthreading is disabled.
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Significant performance decrease (16.96%) when running PGBench under 'normal' load benchmarks in parallel on two VMs when hyperthreading is disabled.
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No significant performance decrease when running Phoronix Test Suite's Pybench and OpenSSL benchmarks in parallel on two VMs when hyperthreading is disabled.
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yum updatewill now install the latestxcp-ng-emu-managerthat fixes the PV guest migration and brings better debug traces in case of crash of the emu-manager binary. We'd be interested if anyone managed to make a migration fail.Testing ideas still at https://github.com/xcp-ng/xcp/wiki/Test-XCP
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@s_mcleod Hi, I'd like to do some basic benchmarks (though not on 8.0.0, but 7.6 still) to compare a host before and after disabling SMT (hyper-threading).
I thought I'd use some hints from your document at https://github.com/sammcj/benchmark_results/tree/master/xcpng/8/hyperthreading_impact
But the "Test 2 - Sysbench Multithreaded Prime Benchmark" link (https://github.com/sammcj/benchmark_results/blob/master/xcpng/8/hyperthreading_impact/hyperthreading_impact/test_2_sysbench_prime.md) returns "404 page not found".
Maybe you'd want to correct the link? Thank you!
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@stormi I just managed to make migration fail using xcp-emu-manager-1.1.1-1 and xcp-ng-generic-lib-1.1.1-1
I have a PVHVM guest (CentOS7) which has static memory limit = 128M/2G and dynamic = 1G/1G and the migration fails after about 20% with a "xenguest invalid argument"
It works if I set static and dynamic max to the same value.Migration of a PVHVM Fedora 28 with static 1G/2G and dynamic 1G/1G works so it's possible it's the 128M static min that's part of the problem in the CentOS case.
A PV CentOS6 with static = 512M/2G and dynamic 1G/1G also works.
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@peder Thanks! Could you make it fail once again and then produce a bug status report on both hosts with
xen-bugtool -yand send the the produced tarballs to the project contact address, or to upload it somewhere temporarily for us to download? -
I just made a try here, I can't reproduce with the same guest OS and memory settings.
Are you also doing Xen Storage motion?
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@stormi I've placed the tarballs here https://student.oedu.se/~peder/xcp-ng/
I changed the static min to 512M, to match the Fedora case, but it still failed.Olivier, I'm not using Xen Storage motion but I am using two old Lenovo L430 Thinkpads as "servers" so that could be part of the problem.
I'll install a new C7 guest and see if the problem persists.
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@olivierlambert The VM that fails migration seems to have been created in xcp-ng 7.6 using the "Other Media" template.
I made a new VM in xcp-ng 8 using the CentOS7 template and I can migrate that just fine with a larger static max. -
Can you provide the full VM record of the problematic one? with
vm param-list uuid=<YOUR FAILING VM UUID>Also the same with the one now working, so I can compare.
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@olivierlambert Sure.
I've put the param-list logs as well as the VMs (sans the Disk) on https://student.oedu.se/~peder/xcp-ng/ -
So I imported your VM metadata in my lab pool, attached to a VM disk with Debian (so we don't really care about the OS) and it worked
I also attached a disk of a previously working CentOS 7 VM, same thing: migration worked
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Weird.
Maybe it's due to the hardware I'm using. I only have 8 GB RAM in the servers but the migration fails even if I'm not running any other VM.
And since it works if static max=dynamic max it shouldn't be a RAM case either.Unless the migration for some reason tries to allocate 2-3 times the amount of RAM if static and dynamic max differ.
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@MajorTom Sorry about that I've been (and still am AFK):
Corrected link: https://github.com/sammcj/benchmark_results/blob/master/xcpng/8/hyperthreading_impact/test_2_sysbench_prime.md
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Folks... was at Citrix event today and the morning was a talk by LoginVSI looking at the impact of the latest security patches for Intel CPU's and the performance impact server on EUC work loads and server scalebility on the Hypervisors. According to the presenter all the Hypervisors (Hyper-V, VMware ESX and XenServer) that they were testing were seeing approx 20-25% decrease in performance when using Intel based systems. What I found interesting was VMware has developed a new scheduler, SCAv2 to help reduce the impact although no numbers where mentioned. There was no mention of anything of th sort for XenServer or HyperV.
https://blogs.vmware.com/performance/2019/05/new-scheduler-option-for-vsphere-6-7-u2.html
According to that blog post .. the impact using the SCAv2 was reduced to 11%.
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This will come in Xen. In fact, work already started. It's called "core scheduling", and this is the preliminary work before sync scheduling, which is a perfect solution (better perfs AND better security) against Intel CPU flaws.
Source: https://lists.xenproject.org/archives/html/xen-devel/2019-05/msg00370.html
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Good to know that they're already working on it for Xen. Surprised that none of the Citrix bod's at the event mentioned it. Looks like the best way to do get around the massive performance hit without switching to AMD !
