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

David S. Ahern
2008-05-17T04:31:24Z

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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

[-- Attachment #2: kvm-stats-rhel3 --]
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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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