linux-kernel - Re: [PATCH 3/3] mm: optimise pte dirty/accessed bit setting by demand based pte insertion

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Date:   Wed, 5 Sep 2018 17:36:18 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ley Foon Tan <lftan@...era.com>,
        nios2-dev@...ts.rocketboards.org
Subject: Re: [PATCH 3/3] mm: optimise pte dirty/accessed bit setting by demand
 based pte insertion

On 09/05/2018 03:18 PM, Nicholas Piggin wrote:
> On Wed, 5 Sep 2018 07:29:51 -0700
> Guenter Roeck <linux@...ck-us.net> wrote:
> 
>> Hi,
>>
>> On Tue, Aug 28, 2018 at 09:20:34PM +1000, Nicholas Piggin wrote:
>>> Similarly to the previous patch, this tries to optimise dirty/accessed
>>> bits in ptes to avoid access costs of hardware setting them.
>>>    
>>
>> This patch results in silent nios2 boot failures, silent meaning that
>> the boot stalls.
>>
>> ...
>> Unpacking initramfs...
>> Freeing initrd memory: 2168K
>> workingset: timestamp_bits=30 max_order=15 bucket_order=0
>> jffs2: version 2.2. (NAND) © 2001-2006 Red Hat, Inc.
>> random: fast init done
>> random: crng init done
>>
>> [no further activity until the qemu session is aborted]
>>
>> Reverting the patch fixes the problem. Bisect log is attached.
> 
> Thanks for bisecting it, I'll try to reproduce. Just qemu with no
> obscure options? Interesting that it's hit nios2 but apparently not
> other archs (yet).
> 

Nothing special. See https://github.com/groeck/linux-build-test/tree/master/rootfs/nios2/.

Guenter