From: Christian Borntraeger <borntraeger@de.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-s390@vger.kernel.org, x86@kernel.org,
linuxppc-dev@lists.ozlabs.org, davem@davemloft.net,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
davej@codemonkey.org.uk
Subject: Re: [PATCH v3 2/3] x86: query dynamic DEBUG_PAGEALLOC setting
Date: Tue, 2 Feb 2016 22:53:36 +0100 [thread overview]
Message-ID: <56B12560.4010201@de.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1602021351290.4977@chino.kir.corp.google.com>
On 02/02/2016 10:51 PM, David Rientjes wrote:
> On Thu, 28 Jan 2016, David Rientjes wrote:
>
>> On Thu, 28 Jan 2016, Christian Borntraeger wrote:
>>
>>> Indeed, I only touched the identity mapping and dump stack.
>>> The question is do we really want to change free_init_pages as well?
>>> The unmapping during runtime causes significant overhead, but the
>>> unmapping after init imposes almost no runtime overhead. Of course,
>>> things get fishy now as what is enabled and what not.
>>>
>>> Kconfig after my patch "mm/debug_pagealloc: Ask users for default setting of debug_pagealloc"
>>> (in mm) now states
>>> ----snip----
>>> By default this option will have a small overhead, e.g. by not
>>> allowing the kernel mapping to be backed by large pages on some
>>> architectures. Even bigger overhead comes when the debugging is
>>> enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
>>> command line parameter.
>>> ----snip----
>>>
>>> So I am tempted to NOT change free_init_pages, but the x86 maintainers
>>> can certainly decide differently. Ingo, Thomas, H. Peter, please advise.
>>>
>>
>> I'm sorry, but I thought the discussion of the previous version of the
>> patchset led to deciding that all CONFIG_DEBUG_PAGEALLOC behavior would be
>> controlled by being enabled on the commandline and checked with
>> debug_pagealloc_enabled().
>>
>> I don't think we should have a CONFIG_DEBUG_PAGEALLOC that does some stuff
>> and then a commandline parameter or CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT
>> to enable more stuff. It should either be all enabled by the commandline
>> (or config option) or split into a separate entity.
>> CONFIG_DEBUG_PAGEALLOC_LIGHT and CONFIG_DEBUG_PAGEALLOC would be fine, but
>> the current state is very confusing about what is being done and what
>> isn't.
>>
>
> Ping?
>
https://lkml.org/lkml/2016/1/29/266
?
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next prev parent reply other threads:[~2016-02-02 21:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-27 10:09 [PATCH v3 0/3] Optimize CONFIG_DEBUG_PAGEALLOC Christian Borntraeger
2016-01-27 10:09 ` [PATCH v3 1/3] mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC Christian Borntraeger
2016-01-27 10:10 ` [PATCH v3 2/3] x86: query dynamic DEBUG_PAGEALLOC setting Christian Borntraeger
2016-01-27 22:17 ` David Rientjes
2016-01-28 9:48 ` Christian Borntraeger
2016-01-28 23:03 ` David Rientjes
2016-02-02 21:51 ` David Rientjes
2016-02-02 21:53 ` Christian Borntraeger [this message]
2016-02-02 22:21 ` Andrew Morton
2016-02-02 22:37 ` Christian Borntraeger
2016-02-02 23:04 ` Andrew Morton
2016-02-03 0:13 ` Stephen Rothwell
2016-02-02 21:52 ` (unknown) David Rientjes via Linuxppc-dev
2016-01-28 23:04 ` (unknown) David Rientjes via Linuxppc-dev
2016-01-27 22:18 ` (unknown) David Rientjes via Linuxppc-dev
2016-01-27 10:10 ` [PATCH v3 3/3] s390: query dynamic DEBUG_PAGEALLOC setting Christian Borntraeger
2016-01-27 22:18 ` David Rientjes
2016-01-27 22:22 ` (unknown) David Rientjes via Linuxppc-dev
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