Re: [Qemu-devel] Windows slow boot: contractor wanted

[Rik van Riel]

On 08/25/2012 01:45 PM, Richard Davies wrote:

> Are you talking about these patches?
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=c67fe3752abe6ab47639e2f9b836900c3dc3da84
> http://marc.info/?l=linux-mm&m=134521289221259
>
> If so, I believe those are in 3.6.0-rc3, so I tested with that.
>
> Unfortunately, I can still get the slow boots and perf top showing
> _raw_spin_lock_irqsave.
>
>
> Here are two perf top traces on 3.6.0-rc3. They do look a bit different from
> 3.5.2, but _raw_spin_lock_irqsave is still at the top:
>
>     PerfTop:   35272 irqs/sec  kernel:98.1%  exact:  0.0% [4000Hz cycles],  
> (all, 16 CPUs)
> ------------------------------------------------------------------------------------------------------------------
>
>      61.85%  [kernel]          [k] _raw_spin_lock_irqsave
>       7.18%  [kernel]          [k] sub_preempt_count
>       5.03%  [kernel]          [k] isolate_freepages_block
>       2.49%  [kernel]          [k] yield_to
>       2.05%  [kernel]          [k] memcmp
>       2.01%  [kernel]          [k] compact_zone
>       1.76%  [kernel]          [k] add_preempt_count
>       1.52%  [kernel]          [k] _raw_spin_lock
>       1.31%  [kernel]          [k] kvm_vcpu_on_spin
>       0.92%  [kernel]          [k] svm_vcpu_run

However, the compaction code is not as prominent as before.

Can you get a backtrace to that _raw_spin_lock_irqsave, to see
from where it is running into lock contention?

It would be good to know whether it is isolate_freepages_block,
yield_to, kvm_vcpu_on_spin or something else...

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