Re: slow boot with 7fef431be9c9 ("mm/page_alloc: place pages to tail in __free_pages_core()")

[David Hildenbrand]

> 8G (with some carve out for the integrated GPU).
> [    0.044181] Memory: 6858688K/7200304K available (14345K kernel code, 9659K rwdata, 4980K rodata, 2484K init, 12292K bss, 341360K reserved, 0K cma-reserved)
>
> Nothing particularly special about these systems that I am aware of.  I'll see if we can repro this issue on any other platforms, but so far, not one has noticed any problems.
>
> > Increasing the boot time from a few seconds to 2-3 minutes does not smell
> > like some corner case cache effects we might be hitting in this particular
> > instance - there have been minor reports that it either slightly increased or
> > slightly decreases initial system performance, but that was about it.
> >
> > Either, yet another latent BUG (but why? why should memory access
> > suddenly be that slow? I could only guess that we are now making sooner
> > use of very slow memory), or there is really something else weird going on.
>
> Looks like pretty much everything is slower based on the timestamps in the dmesg output.  There is a big jump here:

If we're really dealing with some specific slow memory regions and that 
memory gets allocated for something that gets used regularly, then we 
might get a general slowdown. Hard to identify, though :)

> > [    3.758596] ACPI: Added _OSI(Linux-Lenovo-NV-HDMI-Audio)
> > [    3.759372] ACPI: Added _OSI(Linux-HPI-Hybrid-Graphics)
> > [   16.177983] ACPI: 13 ACPI AML tables successfully acquired and loaded
> > [   17.099316] ACPI: [Firmware Bug]: BIOS _OSI(Linux) query ignored
> > [   18.969959] ACPI: EC: EC started
>
> And here:
>
> > [   36.566608] PCI: CLS 64 bytes, default 64
> > [   36.575383] Trying to unpack rootfs image as initramfs...
> > [   44.594348] Initramfs unpacking failed: Decoding failed
> > [   44.765141] Freeing initrd memory: 46348K
>
> Also seeing soft lockups:
> > [  124.588634] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [swapper/1:0]

Yes, I noticed that -- there is a heavy slowdown somewhere.

As that patch is v5.10 already (and we're close to v5.12) I assume 
something is particularly weird about the platform you are running on - 
because this is the first time I see a report like that.

--
Thanks,

David / dhildenb