[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Re: Poor performance on HVM (kernbench)
On Thu, Sep 11, 2008 at 7:26 PM, Gianluca Guida <gianluca.guida@xxxxxxxxxxxxx> wrote: > Or, it could be a fixup table bug, but I doubt it. > > George, did you saw excessive fixup faults in the trace? No, nothing excessive; 273,480 over 30 seconds isn't that bad. The main thing was that out of 15024 attempts to remove writable mappings, 13775 had to fall back to a brute-force search. Looking at the trace, I can't really tell why there should be a problem... I'm seeing tons of circumstances where there should only be one writable mapping, but it falls back to brute-force search anyway. Here's an example: 24.999159660 -x vmexit exit_reason EXCEPTION_NMI eip 2b105dcee330 24.999159660 -x wrmap-bf gfn 7453c 24.999159660 -x fixup va 2b105f000000 gl1e 800000005caf0067 flags (60c)-gp-Pw------ 24.999748980 -x vmentry [...] 24.999759577 -x vmexit exit_reason EXCEPTION_NMI eip ffffffff8022a3b0 24.999759577 -x fixup:unsync va ffff88007453c008 gl1e 7453c067 flags (c000c)-gp------ua- 24.999762562 -x vmentry [...] 25.002946338 -x vmexit exit_reason CR_ACCESS eip ffffffff80491a63 25.002946338 -x wrmap-bf gfn 7e18c 25.002946338 -x oos resync full gfn 7e18c 25.002946338 -x wrmap-bf gfn 7453c 25.002946338 -x oos resync full gfn 7453c 25.003526640 -x vmentry Here we see gfn 7453c: * promoted to be a shadow (the big 'P' in the flag string); at the vmentry, there should be no writable mappings. * marked out-of-sync (one writable mapping, with fixup table) * re-sync'ed because of a CR write, and a brute-force search. Note that the times behind the "wrmap-bf" and "oos resync full" are not valid; but the whole vmexit->vmentry arc takes over 1.5 milliseconds. -George _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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