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SubjectRe: [PATCH v3] xen/balloon: add late_initcall_sync() for initial ballooning done
On Fri, Oct 29, 2021 at 05:46:18PM -0400, Boris Ostrovsky wrote:
>
> On 10/29/21 10:20 AM, Juergen Gross wrote:
> > --- a/Documentation/ABI/stable/sysfs-devices-system-xen_memory
> > +++ b/Documentation/ABI/stable/sysfs-devices-system-xen_memory
> > @@ -84,3 +84,13 @@ Description:
> > Control scrubbing pages before returning them to Xen for others domains
> > use. Can be set with xen_scrub_pages cmdline
> > parameter. Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
> > +
> > +What: /sys/devices/system/xen_memory/xen_memory0/boot_timeout
> > +Date: November 2021
> > +KernelVersion: 5.16
> > +Contact: xen-devel@lists.xenproject.org
> > +Description:
> > + The time (in seconds) to wait before giving up to boot in case
> > + initial ballooning fails to free enough memory. Applies only
> > + when running as HVM or PVH guest and started with less memory
> > + configured than allowed at max.
>
>
> How is this going to be used? We only need this during boot.
>
>
> > - state = update_schedule(state);
> > + balloon_state = update_schedule(balloon_state);
>
>
> Now that balloon_state has whole file scope it can probably be updated inside update_schedule().
>
>
> > + while ((credit = current_credit()) < 0) {
> > + if (credit != last_credit) {
> > + last_changed = jiffies;
> > + last_credit = credit;
> > + }
> > + if (balloon_state == BP_ECANCELED) {
>
>
> What about other states? We are really waiting for BP_DONE, aren't we?

BP_DONE is set also as an intermediate step:

balloon_state = decrease_reservation(n_pages,
GFP_BALLOON);
if (balloon_state == BP_DONE && n_pages != -credit &&
n_pages < totalreserve_pages)
balloon_state = BP_EAGAIN;

It would be bad to finish waiting in this case.

--
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
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