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From: Christoph Hellwig <hch@infradead.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Matthew Wilcox <willy@infradead.org>,
	Christopher Lameter <cl@linux.com>,
	Levin Alexander <Alexander.Levin@microsoft.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Nicolas Boichat <drinkcat@chromium.org>,
	Huaisheng Ye <yehs1@lenovo.com>, Tomasz Figa <tfiga@google.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, Pekka Enberg <penberg@kernel.org>,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	Michal Hocko <mhocko@suse.com>,
	linux-arm-kernel@lists.infradead.org,
	David Rientjes <rientjes@google.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	yingjoe.chen@mediatek.com, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables
Date: Mon, 26 Nov 2018 00:02:13 -0800	[thread overview]
Message-ID: <20181126080213.GA17809@infradead.org> (raw)
In-Reply-To: <555dd63a-0634-6a39-7abc-121e02273cb2@suse.cz>

On Fri, Nov 23, 2018 at 01:23:41PM +0100, Vlastimil Babka wrote:
> Is this also true for caches created by kmem_cache_create(), that
> debugging options can result in not respecting the alignment passed to
> kmem_cache_create()? That would be rather bad, IMHO.

That's what I understood in the discussion.  If not it would make
our live simpler, but would need to be well document.

Christoph can probably explain the alignment choices in slub.

> 
> > But I do agree with the sentiment of not wanting to spread GFP_DMA32
> > futher into the slab allocator.
> 
> I don't see a problem with GFP_DMA32 for custom caches. Generic
> kmalloc() would be worse, since it would have to create a new array of
> kmalloc caches. But that's already ruled out due to the alignment.

True, purely slab probably isn't too bad.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>
Cc: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>,
	Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
	Levin Alexander
	<Alexander.Levin-0li6OtcxBFHby3iVrkZq2A@public.gmane.org>,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	Christopher Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>,
	Nicolas Boichat
	<drinkcat-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Huaisheng Ye <yehs1-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>,
	Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	yingjoe.chen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org,
	Tomasz Figa <tfiga-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Mike Rapoport
	<rppt-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
	Matthias Brugger
	<matthias.bgg-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Joonsoo Kim <iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Pekka Enberg <penberg-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Mel Gorman
	<mgorman-3eNAlZScCAx27rWaFMvyedHuzzzSOjJt@public.gmane.org>
Subject: Re: [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables
Date: Mon, 26 Nov 2018 00:02:13 -0800	[thread overview]
Message-ID: <20181126080213.GA17809@infradead.org> (raw)
In-Reply-To: <555dd63a-0634-6a39-7abc-121e02273cb2-AlSwsSmVLrQ@public.gmane.org>

On Fri, Nov 23, 2018 at 01:23:41PM +0100, Vlastimil Babka wrote:
> Is this also true for caches created by kmem_cache_create(), that
> debugging options can result in not respecting the alignment passed to
> kmem_cache_create()? That would be rather bad, IMHO.

That's what I understood in the discussion.  If not it would make
our live simpler, but would need to be well document.

Christoph can probably explain the alignment choices in slub.

> 
> > But I do agree with the sentiment of not wanting to spread GFP_DMA32
> > futher into the slab allocator.
> 
> I don't see a problem with GFP_DMA32 for custom caches. Generic
> kmalloc() would be worse, since it would have to create a new array of
> kmalloc caches. But that's already ruled out due to the alignment.

True, purely slab probably isn't too bad.

WARNING: multiple messages have this Message-ID (diff)
From: hch@infradead.org (Christoph Hellwig)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables
Date: Mon, 26 Nov 2018 00:02:13 -0800	[thread overview]
Message-ID: <20181126080213.GA17809@infradead.org> (raw)
In-Reply-To: <555dd63a-0634-6a39-7abc-121e02273cb2@suse.cz>

On Fri, Nov 23, 2018 at 01:23:41PM +0100, Vlastimil Babka wrote:
> Is this also true for caches created by kmem_cache_create(), that
> debugging options can result in not respecting the alignment passed to
> kmem_cache_create()? That would be rather bad, IMHO.

That's what I understood in the discussion.  If not it would make
our live simpler, but would need to be well document.

Christoph can probably explain the alignment choices in slub.

> 
> > But I do agree with the sentiment of not wanting to spread GFP_DMA32
> > futher into the slab allocator.
> 
> I don't see a problem with GFP_DMA32 for custom caches. Generic
> kmalloc() would be worse, since it would have to create a new array of
> kmalloc caches. But that's already ruled out due to the alignment.

True, purely slab probably isn't too bad.

  parent reply	other threads:[~2018-11-26  8:02 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-11  9:03 [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables Nicolas Boichat
2018-11-11  9:03 ` Nicolas Boichat
2018-11-11  9:03 ` Nicolas Boichat
2018-11-11  9:03 ` [PATCH v2 1/3] mm: slab/slub: Add check_slab_flags function to check for valid flags Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-11  9:03 ` [PATCH v2 2/3] mm: Add support for SLAB_CACHE_DMA32 Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-21 18:32   ` Christopher Lameter
2018-11-21 18:32     ` Christopher Lameter
2018-11-22  0:52     ` Nicolas Boichat
2018-11-22  0:52       ` Nicolas Boichat
2018-11-22  0:52       ` Nicolas Boichat
2018-11-11  9:03 ` [PATCH v2 3/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-11  9:03   ` Nicolas Boichat
2018-11-21 16:46   ` Will Deacon
2018-11-21 16:46     ` Will Deacon
2018-11-21 17:38     ` Christopher Lameter
2018-11-21 17:38       ` Christopher Lameter
2018-11-21 17:43       ` Robin Murphy
2018-11-21 17:43         ` Robin Murphy
2018-11-21 18:18         ` Christopher Lameter
2018-11-21 18:18           ` Christopher Lameter
2018-11-21 18:02     ` Michal Hocko
2018-11-21 18:02       ` Michal Hocko
2018-11-22  1:20       ` Nicolas Boichat
2018-11-22  1:20         ` Nicolas Boichat
2018-11-22  1:20         ` Nicolas Boichat
2018-11-23 12:15         ` Vlastimil Babka
2018-11-23 12:15           ` Vlastimil Babka
2018-11-21 18:20 ` [PATCH v2 0/3] iommu/io-pgtable-arm-v7s: Use DMA32 zone for page tables Christopher Lameter
2018-11-21 18:20   ` Christopher Lameter
2018-11-21 21:38   ` Matthew Wilcox
2018-11-21 21:38     ` Matthew Wilcox
2018-11-21 21:38     ` Matthew Wilcox
2018-11-21 22:26     ` Robin Murphy
2018-11-21 22:26       ` Robin Murphy
2018-11-21 22:26       ` Robin Murphy
2018-11-22  1:05       ` Nicolas Boichat
2018-11-22  1:05         ` Nicolas Boichat
2018-11-22  1:05         ` Nicolas Boichat
2018-11-22  2:35       ` Matthew Wilcox
2018-11-22  2:35         ` Matthew Wilcox
2018-11-22  2:35         ` Matthew Wilcox
2018-11-22  5:56         ` Nicolas Boichat
2018-11-22  5:56           ` Nicolas Boichat
2018-11-22  5:56           ` Nicolas Boichat
2018-11-22  8:26         ` Christoph Hellwig
2018-11-22  8:26           ` Christoph Hellwig
2018-11-22  8:26           ` Christoph Hellwig
2018-11-22 15:16           ` Matthew Wilcox
2018-11-22 15:16             ` Matthew Wilcox
2018-11-22 15:16             ` Matthew Wilcox
2018-11-22 15:19             ` Christoph Hellwig
2018-11-22 15:19               ` Christoph Hellwig
2018-11-22 15:19               ` Christoph Hellwig
2018-11-22  8:23       ` Christoph Hellwig
2018-11-22  8:23         ` Christoph Hellwig
2018-11-22  8:23         ` Christoph Hellwig
2018-11-23  3:04         ` Nicolas Boichat
2018-11-23  3:04           ` Nicolas Boichat
2018-11-23  3:04           ` Nicolas Boichat
2018-11-23  5:37           ` Nicolas Boichat
2018-11-23  5:37             ` Nicolas Boichat
2018-11-23  5:37             ` Nicolas Boichat
2018-11-23 12:23         ` Vlastimil Babka
2018-11-23 12:23           ` Vlastimil Babka
2018-11-23 12:23           ` Vlastimil Babka
2018-11-23 12:30           ` Michal Hocko
2018-11-23 12:30             ` Michal Hocko
2018-11-23 12:30             ` Michal Hocko
2018-11-26  8:02           ` Christoph Hellwig [this message]
2018-11-26  8:02             ` Christoph Hellwig
2018-11-26  8:02             ` Christoph Hellwig
2018-11-28  8:55             ` Nicolas Boichat
2018-11-28  8:55               ` Nicolas Boichat
2018-11-28  8:55               ` Nicolas Boichat
2018-12-04  9:37 ` Nicolas Boichat
2018-12-04  9:37   ` Nicolas Boichat
2018-12-04 14:35   ` Vlastimil Babka
2018-12-04 14:35     ` Vlastimil Babka
2018-12-04 14:35     ` Vlastimil Babka
2018-12-05  2:04     ` Nicolas Boichat
2018-12-05  2:04       ` Nicolas Boichat
2018-12-05  2:04       ` Nicolas Boichat
2018-12-05  5:51       ` Nicolas Boichat
2018-12-05  5:51         ` Nicolas Boichat
2018-12-05  5:51         ` Nicolas Boichat
2018-12-05 14:41       ` Will Deacon
2018-12-05 14:41         ` Will Deacon
2018-12-05 14:41         ` Will Deacon
2018-12-04 16:28   ` Will Deacon
2018-12-04 16:28     ` Will Deacon
2018-12-04 16:28     ` Will Deacon

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