Re: [PATCH v10 0/3] Per-vCPU dirty quota-based throttling

Shivam Kumar
2024-04-18T10:47:12Z

> On 04-Apr-2024, at 2:49 PM, Marc Zyngier <maz@kernel.org> wrote:
> On Thu, 21 Mar 2024 05:48:01 +0000,
> Shivam Kumar <shivam.kumar1@nutanix.com> wrote:
>>
>>
>>> On 22-Feb-2024, at 1:22 AM, Shivam Kumar <shivam.kumar1@nutanix.com> wrote:
>>>
>>> The current v10 patchset includes the following changes over v9:
>>>
>>> 1. Use vma_pagesize as the dirty granularity for updating dirty quota
>>> on arm64.
>>> 2. Do not update dirty quota for instances where the hypervisor is
>>> writing into guest memory. Accounting for these instances in vCPUs'
>>> dirty quota is unfair to the vCPUs. Also, some of these instances,
>>> such as record_steal_time, frequently try to redundantly mark the same
>>> set of pages dirty again and again. To avoid these distortions, we had
>>> previously relied on checking the dirty bitmap to avoid redundantly
>>> updating quotas. Since we have now decoupled dirty-quota-based
>>> throttling from the live-migration dirty-tracking path, we have
>>> resolved this issue by simply avoiding the mis-accounting caused by
>>> these hypervisor-induced writes to guest memory. Through extensive
>>> experiments, we have verified that this new approach is approximately
>>> as effective as the prior approach that relied on checking the dirty
>>> bitmap.
>>>
>>
>> Hi Marc,
>>
>> I’ve tried my best to address all the concerns raised in the
>> previous patchset. I’d really appreciate it if you could share your
>> thoughts and any feedback you might have on this one.
>
> I'll get to it at some point. However, given that it has you taken the
> best part of a year to respin this, I need to page it all back it,
> which is going to take a bit of time as well.
>
> Thanks,
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
>
No problem. Thank you for acknowledging.

Thanks,
Shivam