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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Xen 4.3 development update / winxp AMD performance regression
On 28/04/13 11:18, Peter Maloney wrote: On 04/25/2013 04:24 PM, Andres Lagar-Cavilla wrote:On Apr 25, 2013, at 10:00 AM, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:On 04/25/2013 02:51 PM, Pasi Kärkkäinen wrote:On Wed, Apr 03, 2013 at 11:34:13AM -0400, Andres Lagar-Cavilla wrote:On Apr 3, 2013, at 6:53 AM, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:On 03/04/13 08:27, Jan Beulich wrote:On 02.04.13 at 18:34, Tim Deegan <tim@xxxxxxx> wrote:At 16:42 +0100 on 02 Apr (1364920927), Jan Beulich wrote:On 02.04.13 at 16:07, George Dunlap <George.Dunlap@xxxxxxxxxxxxx> wrote:* AMD NPT performance regression after c/s 24770:7f79475d3de7 owner: ? Reference: http://marc.info/?l=xen-devel&m=135075376805215This is supposedly fixed with the RTC changes Tim committed the other day. Suravee, is that correct?This is a separate problem. IIRC the AMD XP perf issue is caused by the emulation of LAPIC TPR accesses slowing down with Andres's p2m locking patches. XP doesn't have 'lazy IRQL' or support for CR8, so it takes a _lot_ of vmexits for IRQL reads and writes.Ah, okay, sorry for mixing this up. But how is this a regression then?My sense, when I looked at this back whenever that there was much more to this. The XP IRQL updating is a problem, but it's made terribly worse by the changset in question. It seemed to me like the kind of thing that would be caused by TLB or caches suddenly becoming much less effective.The commit in question does not add p2m mutations, so it doesn't nuke the NPT/EPT TLBs. It introduces a spin lock in the hot path and that is the problem. Later in the 4.2 cycle we changed the common case to use an rwlock. Does the same perf degradation occur with tip of 4.2?Adding Peter to CC who reported the original winxp performance problem/regression on AMD. Peter: Can you try Xen 4.2.2 please and report if it has the performance problem or not?Do you want to compare 4.2.2 to 4.2.1, or 4.3? The changeset in question was included in the initial release of 4.2, so unless you think it's been fixed since, I would expect 4.2 to have this regression.I believe you will see this 4.2 onwards. 4.2 includes the rwlock optimization. Nothing has been added to the tree in that regard recently. AndresBad news... It is very slow still. With 7 vcpus, it took very long to get to the login screen, then I hit the login button at 10:30:30 and at 10.32:10 I can watch my icons starting to appear one by one very slowly. When the icons are all there, I see a blue bar instead of the taskbar. 10:32:47 the taskbar looks normal finally, but systray is still empty. I clicked the start menu at 10:33:40 (still empty systray). At 10:33:54, the start menu opened. At 10:34:20, the first systray icon appeared. at 10:36 I managed to get Task manager loaded, and it shows 88-95% CPU usage in 7 cpus, but doesn't show any processes using much. (xming using 16, System using 11, taskmgr.exe using 9, CCC.exe using 5, explorer and services using 4%, etc.) xm top shows the domain at 646.9% CPU. What guest OS is this again? Windows XP? Do you see the same behavior with other Windows OSes? (e.g., Win7, Win8, w2k3sp2, w2k8?) If you're really keen, you could do a quick xentrace for me after the VM has mostly booted: 1. Run "xentrace -D -e all -S 32 -T 30 /tmp/[name].trace" on your Xen host2. Clone and build the following hg repo: http://xenbits.xen.org/ext/xenalyze 3. Run "xenalyze --svm-mode -s [name].trace > [name].summary" and send me the results -George _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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