Re: performance with guests running 2.4 kernels (specifically RHEL3)

["David S. Ahern" <daahern@cisco.com>]

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Avi Kivity wrote:
> 
> Okay, I committed the patch without the flood count == 5.
> 

I've continued testing the RHEL3 guests with the flood count at 3, and I
am right back to where I started. With the patch and the flood count at
3, I had 2 runs totaling around 24 hours that looked really good. Now, I
am back to square one. I guess the short of it is that I am not sure if
the patch resolves this issue or not.

If you want to back it out, I can continue to apply on my end as I
continue testing. A snapshot of kvm_stat -f 'mmu*' -l is attached for
two test runs with the patch (line wrap is horrible inline).

I will work on creating an ap that will stimulate kscand activity
similar to what I am seeing.


Also, in a prior e-mail I mentioned guest time advancing rapidly. I've
noticed that with the -no-kvm-pit option the guest time is much better
and typically stays within 3 seconds or so of the host, even through the
high kscand activity which is one instance of when I've noticed time
jumps with the kernel pit. Yes, this result has been repeatable through
6 or so runs. :-)

david

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kvm-68 with Avi's patch and flood threshold at 3:


mmio_exit  mmu_cache  mmu_flood  mmu_pde_z  mmu_pte_u  mmu_pte_w  mmu_recyc  mmu_shado
       175        880        880          0       1832       2714          0        880
        35        868        868          0       1782       2650          0        868
        91       8522       8520        131      29179      38651          0       8722
        28        991        992          0       2314       3312          0        992
        91        796        796          0       1648       2445          0        796
        81       1944       1943          0       7241       9213          0       1943
        98       4149       4148         31      11975      16196          0       4214
        41       3379       3380          0       9710      13100          0       3378
        42      17729      17730          0      48415      66152          0      17729

guest has an apparent lockup at this point and when it unfreezes kscand cpu
time jumps on the order of the time command line response was frozen (on the 
order of 30 seconds or more)

        14      18634      18633          0      48286      66921          0      18634
        21      18607      18607          0      48395      67001          0      18607
        91      17991      17991          0      50039      68040          0      17991
         7      17919      17920          0      53731      71650          0      17919
         7      18060      18060          0      53539      71599          0      18060
        21      17755      17755          0      52714      70469          0      17755


-----------------------

with Avi's patch and flood threshold at 5.

 mmio_exit  mmu_cache  mmu_flood  mmu_pde_z  mmu_pte_u  mmu_pte_w  mmu_recyc  mmu_shado
       147        604        602         42      21299      21957          0        660
       112        163        167         23       7567       7759          0        170
       105          0          1          2       3378       3381          0          1
        14          4          4          0       9685       9689          0          4
       137        628        623         43      21557      22255          0        682
        42          0          2          4       5834       5840          0          2
        91         14         16          0      25741      25757          0         16
        28         58         55          0      23571      23626          0         55
        84        627        624         45      32588      33268          0        685
       132          9         13          1      12162      12177          0         13
        91          0          1          0       3422       3423          0          1
        35          1          1          0       4624       4625          0          1
       102        237        244          0      12257      12504          0        242
        19        401        387         46      20643      21088          0        449
        26          3          4          1     127252     127261          0          4


guest has an apparent lockup at this point and when it unfreezes kscand cpu
time jumps on the order of the time command line response was frozen (on the 
order of 30 seconds or more)


        21          0          0          0     182651     182651          0          0
        14          0          0          0     182524     182523          0          0
       178          4          5          4     170752     170759          0          5
        35          0          0          0     181471     181473          0          0
        21          0          0          0     182263     182263          0          0
        14          0          0          0     182493     182494          0          0
        21          0          0          0     182489     182488          0          0
        91          0          0          0     182203     182204          0          0
        35          0          0          0     182378     182377          0          0

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