linux-kernel - Re: [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists

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Date:   Fri, 11 Jun 2021 09:10:52 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Zi Yan <ziy@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored
 on the per-cpu lists

On Thu, Jun 10, 2021 at 07:40:47AM -0400, Zi Yan wrote:
> >> My kernel config is attached and my qemu command is:
> >>
> >> qemu-system-x86_64 -kernel ~/repos/linux-1gb-thp/arch/x86/boot/bzImage \
> >>     -drive file=~/qemu-image/vm.qcow2,if=virtio \
> >>     -append "nokaslr root=/dev/vda1 rw console=ttyS0 " \
> >>     -pidfile vm.pid \
> >>     -netdev user,id=mynet0,hostfwd=tcp::11022-:22 \
> >>     -device virtio-net-pci,netdev=mynet0 \
> >>     -m 16g -smp 6 -cpu host -enable-kvm -nographic \
> >>     -machine hmat=on -object memory-backend-ram,size=8g,id=m0 \
> >>     -object memory-backend-ram,size=8g,id=m1 \
> >>     -numa node,memdev=m0,nodeid=0 -numa node,memdev=m1,nodeid=1
> >>
> >> The attached config has THP disabled. The VM cannot boot with THP enabled,
> >> either.
> >>
> >
> > There is not a lot of information to go on here. Can you confirm that a
> > revert of that specific patch from mmotm-2021-06-07-18-33 also boots? It
> > sounds like your console log is empty, does anything useful appear if
> > you add "earlyprintk=serial,ttyS0,115200" to the kernel command line?
> 
> Sure. I can confirm that reverting the patch makes the VM boot.
> The important information I forgot to mention is that after I remove
> the NUMA setting in the QEMU, the VM can boot too.
> 
> earlyprintk gave the error message (page out of zone boundary) when the VM could not boot:
> 

Ok, thanks, that helps. For a page to be out of boundary, I either have
completely screwed the zone handling for PCP or, more likely, pages are
leaking onto the boot pagesets because of the batch count handling. It's
weird I did not see this on NUMA machines but nevertheless, I'll go
find it. It should not take long.

-- 
Mel Gorman
SUSE Labs