Hi, Alex
Sorry for late.
I found your problem(boot time difference w/ PAL_HALT_LIGHT emulation patch)
occurred in SMP(credit).
But, it does not occurred in UP, SMP(bvt) and SMP(credit w/ affinity).
I think the emulation of pal_halt_light for domU
does not good work for DomVTI boot up
under credit scheduling w/o affinity.
And consider the Xiantao survey,
qemu make heavy I/O operations at the boot up.
Consider the above two conditions,
I think credit scheduler algorithm does not consider
the block state.(caused by pal_halt_light emulation)
So I want to switch off the vcpu migration at heavy load
I planned as follows.
1)In the short term,
I want to avoid this problem by
HALT the PAL_HALT_LIGHT emulation while DomVTI boot up.
or
Lock VCPUs migrations while DomVTI boot up.
(when Credit scheduler runs)
2)In the long term,
I will make a patch to avoid this problem.
(Consider the heavy io w/ vcpu migration)
N.B.
I checked under CS:10559.(original patch made)
Thanks,
Atsushi SAKAI
>On Tue, 2006-07-11 at 19:42 +0800, Zhang, Xiantao wrote:
>> Hi Alex,
>> Seems this issue was caused by Cset 10688. In vcpu_itr_d, the current
>> logic purges vhpt with cpu_flush_vhpt_range but it is very heavy to
>> xen0. When creating VTi domain @ early stage, IO operation is very
>> excessive, so qemu was scheduled out and in very frequently and this
>> logic was executed every time. In addition, cpu_flush_vhpt_range using
>> identity map to purge vhpt may cause more tlb miss due to no TR map.
>> If remove vcpu_flush_tlb_vhpt_range logic although it definitely
>> needed, seems VTi becomes healthy. Maybe potential bugs exist there.:)
>
> Thanks for investigating Xiantao. Isaku, any thoughts on how to
>regain VTI performance? Thanks,
>
> Alex
>
>--
>Alex Williamson HP Open Source & Linux Org.
>
>
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