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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 17 Jun 2021 08:01:44 -0700
Message-ID: <CAHk-=wjgg67NMBNG99naEQ1cM0mXBBzdhCJaYFH-kC+mLK+J2g@mail.gmail.com>
Subject: Re: Linux 5.13-rc6 regression to 5.12.x: kernel OOM and panic during
 kernel boot in low memory Xen VM's (256MB assigned memory).
To:     Sander Eikelenboom <linux@eikelenboom.it>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
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On Thu, Jun 17, 2021 at 2:26 AM Sander Eikelenboom <linux@eikelenboom.it> wrote:
>
> I just tried to upgrade and test the linux kernel going from the 5.12 kernel series to 5.13-rc6 on my homeserver with Xen, but ran in some trouble.
>
> Some VM's boot fine (with more than 256MB memory assigned), but the smaller (memory wise) PVH ones crash during kernel boot due to OOM.
> Booting VM's with 5.12(.9) kernel still works fine, also when dom0 is running 5.13-rc6 (but it has more memory assigned, so that is not unexpected).

Adding Rasmus to the cc, because this looks kind of like the async
roofs population thing that caused some other oom issues too.

Rasmus? Original report here:

   https://lore.kernel.org/lkml/ee8bf04c-6e55-1d9b-7bdb-25e6108e8e1e@eikelenboom.it/

I do find it odd that we'd be running out of memory so early..

        Linus