From: "Andreas Krebbel1" <Andreas.Krebbel@de.ibm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
kbuild test robot <fengguang.wu@intel.com>,
heicars2@linux.vnet.ibm.com, kbuild-all@01.org,
Linux Memory Management List <linux-mm@kvack.org>,
mschwid2@linux.vnet.ibm.com
Subject: Re: [linux-next:master 12891/13017] mm/slub.c:2396:1: warning: '___slab_alloc' uses dynamic stack allocation
Date: Fri, 13 Nov 2015 16:32:33 +0100 [thread overview]
Message-ID: <201511131533.tADFXTGY001678@d06av05.portsmouth.uk.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1511130919240.15385@east.gentwo.org>
> On Fri, 13 Nov 2015, Andreas Krebbel1 wrote:
>
> > this appears to be the result of aligning struct page to more than 8
bytes
> > and putting it onto the stack - wich is only 8 bytes aligned. The
> > compiler has to perform runtime alignment to achieve that. It
allocates
> > memory using *alloca* and does the math with the returned pointer. Our
> > dynamic stack allocation option basically only checks if there is an
> > alloca user.
>
> The slub uses of struct page only require an alignment of the page
struct
> on the stack to a word. So its fine.
Our compare and swap double hardware instruction unfortunately requires 16
byte alignment. That's probably the reason why this alignment has been
picked. So I don't think that we can easily get rid of it.
-Andreas-
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next prev parent reply other threads:[~2015-11-13 15:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-11 6:34 kbuild test robot
2015-11-11 20:41 ` Andrew Morton
2015-11-13 11:52 ` Martin Schwidefsky
2015-11-13 15:13 ` Andreas Krebbel1
[not found] ` <201511131513.tADFDwJN030997@d06av03.portsmouth.uk.ibm.com>
2015-11-13 15:22 ` Christoph Lameter
2015-11-13 15:32 ` Andreas Krebbel1 [this message]
[not found] ` <201511131532.tADFWgYs000305@d06av09.portsmouth.uk.ibm.com>
2015-11-13 17:05 ` Christoph Lameter
[not found] ` <201511131414.tADEE1co028795@d06av10.portsmouth.uk.ibm.com>
2015-11-16 8:47 ` Martin Schwidefsky
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