Messages in this thread | | | Date | Thu, 4 Nov 2021 12:34:56 -0400 | Subject | Re: [PATCH v4] xen/balloon: add late_initcall_sync() for initial ballooning done | From | Boris Ostrovsky <> |
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On 11/4/21 12:21 PM, Juergen Gross wrote: > On 04.11.21 16:55, Boris Ostrovsky wrote: >> >> On 11/3/21 9:55 PM, Boris Ostrovsky wrote: >>> >>> On 11/2/21 5:19 AM, Juergen Gross wrote: >>>> When running as PVH or HVM guest with actual memory < max memory the >>>> hypervisor is using "populate on demand" in order to allow the guest >>>> to balloon down from its maximum memory size. For this to work >>>> correctly the guest must not touch more memory pages than its target >>>> memory size as otherwise the PoD cache will be exhausted and the guest >>>> is crashed as a result of that. >>>> >>>> In extreme cases ballooning down might not be finished today before >>>> the init process is started, which can consume lots of memory. >>>> >>>> In order to avoid random boot crashes in such cases, add a late init >>>> call to wait for ballooning down having finished for PVH/HVM guests. >>>> >>>> Warn on console if initial ballooning fails, panic() after stalling >>>> for more than 3 minutes per default. Add a module parameter for >>>> changing this timeout. >>>> >>>> Cc: <stable@vger.kernel.org> >>>> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> >>>> Signed-off-by: Juergen Gross <jgross@suse.com> >>> >>> >>> >>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> >> >> >> This appears to have noticeable effect on boot time (and boot experience in general). >> >> >> I have >> >> >> memory=1024 >> maxmem=8192 >> >> >> And my boot time (on an admittedly slow box) went from 33 to 45 seconds. And boot pauses in the middle while it is waiting for ballooning to complete. >> >> >> [ 5.062714] xen:balloon: Waiting for initial ballooning down having finished. >> [ 5.449696] random: crng init done >> [ 34.613050] xen:balloon: Initial ballooning down finished. > > This shows that before it was just by chance that the PoD cache wasn't > exhausted.
True.
> >> So at least I think we should consider bumping log level down from info. > > Which level would you prefer? warn? >
Notice? Although that won't make much difference as WARN is the default level.
I suppose we can't turn scrubbing off at this point?
> And if so, would you mind doing this while committing (I have one day > off tomorrow)?
Yes, of course.
-boris
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