Re: [PATCH RFC 1/3] mm: When CONFIG_ZONE_DMA32 is set, use DMA32 for SLAB_CACHE_DMA
On 11/9/18 12:57 PM, Nicolas Boichat wrote: > On Fri, Nov 9, 2018 at 6:43 PM Vlastimil Babka wrote: >> Also I'm probably missing the point of this all. In patch 3 you use >> __get_dma32_pages() thus __get_free_pages(__GFP_DMA32), which uses >> alloc_pages, thus the page allocator directly, and there's no slab >> caches involved. > > __get_dma32_pages fixes level 1 page allocations in the patch 3. > > This change fixes level 2 page allocations > (kmem_cache_zalloc(data->l2_tables, gfp | GFP_DMA)), by transparently > remapping GFP_DMA to an underlying ZONE_DMA32. > > The alternative would be to create a new SLAB_CACHE_DMA32 when > CONFIG_ZONE_DMA32 is defined, but then I'm concerned that the callers > would need to choose between the 2 (GFP_DMA or GFP_DMA32...), and also > need to use some ifdefs (but maybe that's not a valid concern?). > >> It makes little sense to involve slab for page table >> allocations anyway, as those tend to be aligned to a page size (or >> high-order page size). So what am I missing? > > Level 2 tables are ARM_V7S_TABLE_SIZE(2) => 1kb, so we'd waste 3kb if > we allocated a full page. Oh, I see. Well, I think indeed the most transparent would be to support SLAB_CACHE_DMA32. The callers of kmem_cache_zalloc() would then need not add anything special to gfp, as that's stored internally upon kmem_cache_create(). Of course SLAB_BUG_MASK would no longer have to treat __GFP_DMA32 as unexpected. It would be unexpected when passed to kmalloc() which doesn't have special dma32 caches, but for a cache explicitly created to allocate from ZONE_DMA32, I don't see why not. I'm somewhat surprised that there wouldn't be a need for this earlier, so maybe I'm still missing something. > Thanks, > ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH RFC 1/3] mm: When CONFIG_ZONE_DMA32 is set, use DMA32 for SLAB_CACHE_DMA
On Fri, Nov 9, 2018 at 6:43 PM Vlastimil Babka wrote:
>
> On 11/9/18 9:24 AM, Nicolas Boichat wrote:
> > Some callers, namely iommu/io-pgtable-arm-v7s, expect the physical
> > address returned by kmem_cache_alloc with GFP_DMA parameter to be
> > a 32-bit address.
> >
> > Instead of adding a separate SLAB_CACHE_DMA32 (and then audit
> > all the calls to check if they require memory from DMA or DMA32
> > zone), we simply allocate SLAB_CACHE_DMA cache in DMA32 region,
> > if CONFIG_ZONE_DMA32 is set.
> >
> > Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
> > Signed-off-by: Nicolas Boichat
> > ---
> > include/linux/slab.h | 13 -
> > mm/slab.c| 2 +-
> > mm/slub.c| 2 +-
> > 3 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 918f374e7156f4..390afe90c5dec0 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -30,7 +30,7 @@
> > #define SLAB_POISON ((slab_flags_t __force)0x0800U)
> > /* Align objs on cache lines */
> > #define SLAB_HWCACHE_ALIGN ((slab_flags_t __force)0x2000U)
> > -/* Use GFP_DMA memory */
> > +/* Use GFP_DMA or GFP_DMA32 memory */
> > #define SLAB_CACHE_DMA ((slab_flags_t __force)0x4000U)
> > /* DEBUG: Store the last owner for bug hunting */
> > #define SLAB_STORE_USER ((slab_flags_t __force)0x0001U)
> > @@ -126,6 +126,17 @@
> > #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
> > (unsigned long)ZERO_SIZE_PTR)
> >
> > +/*
> > + * When ZONE_DMA32 is defined, have SLAB_CACHE_DMA allocate memory with
> > + * GFP_DMA32 instead of GFP_DMA, as this is what some of the callers
> > + * require (instead of duplicating cache for DMA and DMA32 zones).
> > + */
> > +#ifdef CONFIG_ZONE_DMA32
> > +#define SLAB_CACHE_DMA_GFP GFP_DMA32
> > +#else
> > +#define SLAB_CACHE_DMA_GFP GFP_DMA
> > +#endif
>
> AFAICS this will break e.g. x86 which can have both ZONE_DMA and
> ZONE_DMA32, and now you would make kmalloc(__GFP_DMA) return objects
> from ZONE_DMA32 instead of __ZONE_DMA, which can break something.
Oh, I was not aware that both ZONE_DMA and ZONE_DMA32 can be defined
at the same time. I guess the test should be inverted, something like
this (can be simplified...):
#ifdef CONFIG_ZONE_DMA
#define SLAB_CACHE_DMA_GFP GFP_DMA
#elif defined(CONFIG_ZONE_DMA32)
#define SLAB_CACHE_DMA_GFP GFP_DMA32
#else
#define SLAB_CACHE_DMA_GFP GFP_DMA // ?
#endif
> Also I'm probably missing the point of this all. In patch 3 you use
> __get_dma32_pages() thus __get_free_pages(__GFP_DMA32), which uses
> alloc_pages, thus the page allocator directly, and there's no slab
> caches involved.
__get_dma32_pages fixes level 1 page allocations in the patch 3.
This change fixes level 2 page allocations
(kmem_cache_zalloc(data->l2_tables, gfp | GFP_DMA)), by transparently
remapping GFP_DMA to an underlying ZONE_DMA32.
The alternative would be to create a new SLAB_CACHE_DMA32 when
CONFIG_ZONE_DMA32 is defined, but then I'm concerned that the callers
would need to choose between the 2 (GFP_DMA or GFP_DMA32...), and also
need to use some ifdefs (but maybe that's not a valid concern?).
> It makes little sense to involve slab for page table
> allocations anyway, as those tend to be aligned to a page size (or
> high-order page size). So what am I missing?
Level 2 tables are ARM_V7S_TABLE_SIZE(2) => 1kb, so we'd waste 3kb if
we allocated a full page.
Thanks,
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Re: [PATCH RFC 1/3] mm: When CONFIG_ZONE_DMA32 is set, use DMA32 for SLAB_CACHE_DMA
On 11/9/18 9:24 AM, Nicolas Boichat wrote:
> Some callers, namely iommu/io-pgtable-arm-v7s, expect the physical
> address returned by kmem_cache_alloc with GFP_DMA parameter to be
> a 32-bit address.
>
> Instead of adding a separate SLAB_CACHE_DMA32 (and then audit
> all the calls to check if they require memory from DMA or DMA32
> zone), we simply allocate SLAB_CACHE_DMA cache in DMA32 region,
> if CONFIG_ZONE_DMA32 is set.
>
> Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
> Signed-off-by: Nicolas Boichat
> ---
> include/linux/slab.h | 13 -
> mm/slab.c| 2 +-
> mm/slub.c| 2 +-
> 3 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 918f374e7156f4..390afe90c5dec0 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -30,7 +30,7 @@
> #define SLAB_POISON ((slab_flags_t __force)0x0800U)
> /* Align objs on cache lines */
> #define SLAB_HWCACHE_ALIGN ((slab_flags_t __force)0x2000U)
> -/* Use GFP_DMA memory */
> +/* Use GFP_DMA or GFP_DMA32 memory */
> #define SLAB_CACHE_DMA ((slab_flags_t __force)0x4000U)
> /* DEBUG: Store the last owner for bug hunting */
> #define SLAB_STORE_USER ((slab_flags_t __force)0x0001U)
> @@ -126,6 +126,17 @@
> #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
> (unsigned long)ZERO_SIZE_PTR)
>
> +/*
> + * When ZONE_DMA32 is defined, have SLAB_CACHE_DMA allocate memory with
> + * GFP_DMA32 instead of GFP_DMA, as this is what some of the callers
> + * require (instead of duplicating cache for DMA and DMA32 zones).
> + */
> +#ifdef CONFIG_ZONE_DMA32
> +#define SLAB_CACHE_DMA_GFP GFP_DMA32
> +#else
> +#define SLAB_CACHE_DMA_GFP GFP_DMA
> +#endif
AFAICS this will break e.g. x86 which can have both ZONE_DMA and
ZONE_DMA32, and now you would make kmalloc(__GFP_DMA) return objects
from ZONE_DMA32 instead of __ZONE_DMA, which can break something.
Also I'm probably missing the point of this all. In patch 3 you use
__get_dma32_pages() thus __get_free_pages(__GFP_DMA32), which uses
alloc_pages, thus the page allocator directly, and there's no slab
caches involved. It makes little sense to involve slab for page table
allocations anyway, as those tend to be aligned to a page size (or
high-order page size). So what am I missing?
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[PATCH RFC 1/3] mm: When CONFIG_ZONE_DMA32 is set, use DMA32 for SLAB_CACHE_DMA
Some callers, namely iommu/io-pgtable-arm-v7s, expect the physical
address returned by kmem_cache_alloc with GFP_DMA parameter to be
a 32-bit address.
Instead of adding a separate SLAB_CACHE_DMA32 (and then audit
all the calls to check if they require memory from DMA or DMA32
zone), we simply allocate SLAB_CACHE_DMA cache in DMA32 region,
if CONFIG_ZONE_DMA32 is set.
Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
Signed-off-by: Nicolas Boichat
---
include/linux/slab.h | 13 -
mm/slab.c| 2 +-
mm/slub.c| 2 +-
3 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 918f374e7156f4..390afe90c5dec0 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -30,7 +30,7 @@
#define SLAB_POISON((slab_flags_t __force)0x0800U)
/* Align objs on cache lines */
#define SLAB_HWCACHE_ALIGN ((slab_flags_t __force)0x2000U)
-/* Use GFP_DMA memory */
+/* Use GFP_DMA or GFP_DMA32 memory */
#define SLAB_CACHE_DMA ((slab_flags_t __force)0x4000U)
/* DEBUG: Store the last owner for bug hunting */
#define SLAB_STORE_USER((slab_flags_t __force)0x0001U)
@@ -126,6 +126,17 @@
#define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
(unsigned long)ZERO_SIZE_PTR)
+/*
+ * When ZONE_DMA32 is defined, have SLAB_CACHE_DMA allocate memory with
+ * GFP_DMA32 instead of GFP_DMA, as this is what some of the callers
+ * require (instead of duplicating cache for DMA and DMA32 zones).
+ */
+#ifdef CONFIG_ZONE_DMA32
+#define SLAB_CACHE_DMA_GFP GFP_DMA32
+#else
+#define SLAB_CACHE_DMA_GFP GFP_DMA
+#endif
+
#include
struct mem_cgroup;
diff --git a/mm/slab.c b/mm/slab.c
index 2a5654bb3b3ff3..8810daa052dcdc 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2121,7 +2121,7 @@ int __kmem_cache_create(struct kmem_cache *cachep,
slab_flags_t flags)
cachep->flags = flags;
cachep->allocflags = __GFP_COMP;
if (flags & SLAB_CACHE_DMA)
- cachep->allocflags |= GFP_DMA;
+ cachep->allocflags |= SLAB_CACHE_DMA_GFP;
if (flags & SLAB_RECLAIM_ACCOUNT)
cachep->allocflags |= __GFP_RECLAIMABLE;
cachep->size = size;
diff --git a/mm/slub.c b/mm/slub.c
index e3629cd7aff164..fdd05323e54cbd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3575,7 +3575,7 @@ static int calculate_sizes(struct kmem_cache *s, int
forced_order)
s->allocflags |= __GFP_COMP;
if (s->flags & SLAB_CACHE_DMA)
- s->allocflags |= GFP_DMA;
+ s->allocflags |= SLAB_CACHE_DMA_GFP;
if (s->flags & SLAB_RECLAIM_ACCOUNT)
s->allocflags |= __GFP_RECLAIMABLE;
--
2.19.1.930.g4563a0d9d0-goog
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