Re: [PATCH] mapletree-vs-khugepaged

From: Liam Howlett <liam.howlett@oracle.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Heiko Carstens <hca@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mapletree-vs-khugepaged
Date: Thu, 19 May 2022 22:38:56 +0000	[thread overview]
Message-ID: <20220519223848.wp77de6ohc744hek@revolver> (raw)
In-Reply-To: <28f3958f-dd25-cb1a-0a4c-040e7706ffc7@roeck-us.net>

* Guenter Roeck <linux@roeck-us.net> [220519 17:42]:
> On 5/19/22 07:35, Liam Howlett wrote:
> > * Guenter Roeck <linux@roeck-us.net> [220517 10:32]:
> > 
> > ...
> > > 
> > > Another bisect result, boot failures with nommu targets (arm:mps2-an385,
> > > m68k:mcf5208evb). Bisect log is the same for both.
> > ...
> > > # first bad commit: [bd773a78705fb58eeadd80e5b31739df4c83c559] nommu: remove uses of VMA linked list
> > 
> > I cannot reproduce this on my side, even with that specific commit.  Can
> > you point me to the failure log, config file, etc?  Do you still see
> > this with the fixes I've sent recently?
> > 
> 
> This was in linux-next; most recently with next-20220517.
> I don't know if that was up-to-date with your patches.
> The problem seems to be memory allocation failures.
> A sample log is at
> https://kerneltests.org/builders/qemu-m68k-next/builds/1065/steps/qemubuildcommand/logs/stdio
> The log history at
> https://kerneltests.org/builders/qemu-m68k-next?numbuilds=30
> will give you a variety of logs.

I did hunt that down.  It looks like it's allocating 512kb and failing.
I tried the commit you see the failures on and my qemu boots fine.

> 
> The configuration is derived from m5208evb_defconfig, with initrd
> and command line embedded in the image. You can see the detailed
> configuration updates at
> https://github.com/groeck/linux-build-test/blob/master/rootfs/m68k/run-qemu-m68k.sh
> 
> Qemu command line is
> 
> qemu-system-m68k -M mcf5208evb -kernel vmlinux \
>     -cpu m5208 -no-reboot -nographic -monitor none
>     -append "rdinit=/sbin/init console=ttyS0,115200"
> 
> with initrd from
> https://github.com/groeck/linux-build-test/blob/master/rootfs/m68k/rootfs-5208.cpio.gz

I'm using buildroot-2022.02.1, so maybe that's the difference?
Buildroot has the following qemu line:

qemu-system-m68k -M mcf5208evb -cpu m5208 -kernel vmlinux -nographic

> 
> I use qemu v6.2, but any recent qemu version should work.
> 
> Hope this helps,
> Guenter

Thanks for the information.  I will keep digging into it.
Liam