From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: David Rientjes <rientjes@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-s390@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting
Date: Wed, 27 Jan 2016 09:59:21 +0900 [thread overview]
Message-ID: <20160127005920.GB7089@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <alpine.DEB.2.10.1601261633520.6121@chino.kir.corp.google.com>
On Tue, Jan 26, 2016 at 04:36:11PM -0800, David Rientjes wrote:
> On Wed, 27 Jan 2016, Joonsoo Kim wrote:
>
> > > I'd agree if CONFIG_DEBUG_PAGEALLOC only did anything when
> > > debug_pagealloc_enabled() is true, but that doesn't seem to be the case.
> > > When CONFIG_DEBUG_SLAB is enabled, for instance, CONFIG_DEBUG_PAGEALLOC
> > > also enables stackinfo storing and poisoning and it's not guarded by
> > > debug_pagealloc_enabled().
> > >
> > > It seems like CONFIG_DEBUG_PAGEALLOC enables debugging functionality
> > > outside the scope of the debug_pagealloc=on kernel parameter, so
> > > DEBUG_PAGEALLOC(disabled) actually does mean something.
> >
> > Hello, David.
> >
> > I tried to fix CONFIG_DEBUG_SLAB case on 04/16 of following patchset.
> >
> > http://thread.gmane.org/gmane.linux.kernel.mm/144527
> >
> > I found that there are more sites to fix but not so many.
> > We can do it.
> >
>
> For the slab case, sure, this can be fixed, but there is other code that
> uses CONFIG_DEBUG_PAGEALLOC to suggest debugging is always enabled and is
> indifferent to debug_pagealloc_enabled(). I find this in powerpc and
> sparc arch code as well as generic vmalloc code.
Yes, I also found it.
>
> If we can convert existing users that only check for
> CONFIG_DEBUG_PAGEALLOC to rather check for debug_pagealloc_enabled() and
> agree that it is only enabled for debug_pagealloc=on, then this would seem
> fine. However, I think we should at least consult with those users before
> removing an artifact from the kernel log that could be useful in debugging
> why a particular BUG() happened.
Yes, at least, non-architecture dependent code (vmalloc, SLAB, SLUB) should
be changed first. If Christian doesn't mind, I will try to fix above 3
things.
Thanks.
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next prev parent reply other threads:[~2016-01-27 0:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-26 9:18 [PATCH/RFC 0/3] Optimize CONFIG_DEBUG_PAGEALLOC Christian Borntraeger
2016-01-26 9:18 ` [PATCH/RFC 1/3] mm: provide debug_pagealloc_enabled() without CONFIG_DEBUG_PAGEALLOC Christian Borntraeger
2016-01-26 23:23 ` David Rientjes
2016-01-26 9:18 ` [PATCH/RFC 2/3] x86: query dynamic DEBUG_PAGEALLOC setting Christian Borntraeger
2016-01-26 9:18 ` [PATCH/RFC 3/3] s390: " Christian Borntraeger
2016-01-26 18:19 ` Heiko Carstens
2016-01-26 20:38 ` Thomas Gleixner
2016-01-26 23:29 ` David Rientjes
2016-01-27 0:19 ` Joonsoo Kim
2016-01-27 0:36 ` David Rientjes
2016-01-27 0:59 ` Joonsoo Kim [this message]
2016-01-27 7:59 ` Christian Borntraeger
2016-01-27 12:41 ` Vlastimil Babka
2016-01-27 12:47 ` Christian Borntraeger
2016-01-27 13:03 ` Vlastimil Babka
2016-01-27 13:09 ` Christian Borntraeger
2016-01-28 4:25 ` Joonsoo Kim
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