RE: [PATCH 6/9] drivers: add Contiguous Memory Allocator
Hello, On Tuesday, October 18, 2011 3:43 PM Mel Gorman wrote: > On Thu, Oct 06, 2011 at 03:54:46PM +0200, Marek Szyprowski wrote: > > The Contiguous Memory Allocator is a set of helper functions for DMA > > mapping framework that improves allocations of contiguous memory chunks. > > > > CMA grabs memory on system boot, marks it with CMA_MIGRATE_TYPE and > > gives back to the system. Kernel is allowed to allocate movable pages > > within CMA's managed memory so that it can be used for example for page > > cache when DMA mapping do not use it. On dma_alloc_from_contiguous() > > request such pages are migrated out of CMA area to free required > > contiguous block and fulfill the request. This allows to allocate large > > contiguous chunks of memory at any time assuming that there is enough > > free memory available in the system. > > > > This code is heavily based on earlier works by Michal Nazarewicz. > > > > Signed-off-by: Marek Szyprowski > > Signed-off-by: Kyungmin Park > > CC: Michal Nazarewicz > > --- > > arch/Kconfig |3 + > > drivers/base/Kconfig | 79 +++ > > drivers/base/Makefile|1 + > > drivers/base/dma-contiguous.c| 386 > > ++ > > include/asm-generic/dma-contiguous.h | 27 +++ > > include/linux/device.h |4 + > > include/linux/dma-contiguous.h | 106 ++ > > 7 files changed, 606 insertions(+), 0 deletions(-) > > create mode 100644 drivers/base/dma-contiguous.c > > create mode 100644 include/asm-generic/dma-contiguous.h > > create mode 100644 include/linux/dma-contiguous.h > > > > diff --git a/arch/Kconfig b/arch/Kconfig > > index 4b0669c..a3b39a2 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -124,6 +124,9 @@ config HAVE_ARCH_TRACEHOOK > > config HAVE_DMA_ATTRS > > bool > > > > +config HAVE_DMA_CONTIGUOUS > > + bool > > + > > config USE_GENERIC_SMP_HELPERS > > bool > > > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > > index 21cf46f..a5e6d75 100644 > > --- a/drivers/base/Kconfig > > +++ b/drivers/base/Kconfig > > @@ -174,4 +174,83 @@ config SYS_HYPERVISOR > > > > source "drivers/base/regmap/Kconfig" > > > > +config CMA > > + bool "Contiguous Memory Allocator (EXPERIMENTAL)" > > + depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK && EXPERIMENTAL > > + select MIGRATION > > + select CMA_MIGRATE_TYPE > > + help > > + This enables the Contiguous Memory Allocator which allows drivers > > + to allocate big physically-contiguous blocks of memory for use with > > + hardware components that do not support I/O map nor scatter-gather. > > + > > + For more information see . > > + If unsure, say "n". > > + > > +if CMA > > + > > +config CMA_DEBUG > > + bool "CMA debug messages (DEVELOPEMENT)" > > s/DEVELOPEMENT/DEVELOPMENT/ > > Should it be under DEBUG_KERNEL? > > > + help > > + Turns on debug messages in CMA. This produces KERN_DEBUG > > + messages for every CMA call as well as various messages while > > + processing calls such as dma_alloc_from_contiguous(). > > + This option does not affect warning and error messages. > > + > > +comment "Default contiguous memory area size:" > > + > > +config CMA_SIZE_ABSOLUTE > > + int "Absolute size (in MiB)" > > + depends on !CMA_SIZE_SEL_PERCENTAGE > > + default 16 > > + help > > + Defines the size (in MiB) of the default memory area for Contiguous > > + Memory Allocator. > > + > > +config CMA_SIZE_PERCENTAGE > > + int "Percentage of total memory" > > + depends on !CMA_SIZE_SEL_ABSOLUTE > > + default 10 > > + help > > + Defines the size of the default memory area for Contiguous Memory > > + Allocator as a percentage of the total memory in the system. > > + > > Why is this not a kernel parameter rather than a config option? There is also a kernel parameter for CMA area size which overrides the value from .config. > Better yet, why do drivers not register how much CMA memory they are > interested in and then the drive core figure out if it can allocate that > much or not? CMA area is reserved very early during boot process, even before the buddy allocator gets initialized. That time no device driver has been probed yet. Such early reservation is required to be sure that enough contiguous memory can be gathered and to perform some MMU related fixups that are required on ARM to avoid page aliasing for dma_alloc_coherent() memory. > > +choice > > + prompt "Selected region size" > > + default CMA_SIZE_SEL_ABSOLUTE > > + > > +config CMA_SIZE_SEL_ABSOLUTE > > + bool "Use absolute value only" > > + > > +config CMA_SIZE_SEL_PERCENTAGE > > + bool "Use percentage value only" > > + > > +config CMA_SIZE_SEL_MIN > > + bool "Use lower value (minimum)" > > + > > +config CMA_SIZE_SEL_MAX > > + bool "Use higher value (maximum)" > > + > > +endchoice > > + > > +config CMA_ALIGNMENT > > + int "Max
Re: [PATCH 6/9] drivers: add Contiguous Memory Allocator
On Thu, Oct 06, 2011 at 03:54:46PM +0200, Marek Szyprowski wrote:
+static unsigned long __init __cma_early_get_total_pages(void)
+{
+ struct memblock_region *reg;
+ unsigned long total_pages = 0;
+
+ /*
+* We cannot use memblock_phys_mem_size() here, because
+* memblock_analyze() has not been called yet.
+*/
+ for_each_memblock(memory, reg)
+ total_pages += memblock_region_memory_end_pfn(reg) -
+ memblock_region_memory_base_pfn(reg);
+ return total_pages;
+}
+
On Tue, 18 Oct 2011 06:43:21 -0700, Mel Gorman wrote:
Is this being called too early yet? What prevents you seeing up the CMA
regions after the page allocator is brought up for example? I understand
that there is a need for the memory to be coherent so maybe that is the
obstacle.
Another reason is that we want to be sure that we can get given range of pages.
After page allocator is set-up, someone could allocate a non-movable page from
the range that interests us and that wouldn't be nice for us.
+struct page *dma_alloc_from_contiguous(struct device *dev, int count,
+ unsigned int align)
+{
+ struct cma *cma = get_dev_cma_area(dev);
+ unsigned long pfn, pageno;
+ int ret;
+
+ if (!cma)
+ return NULL;
+
+ if (align > CONFIG_CMA_ALIGNMENT)
+ align = CONFIG_CMA_ALIGNMENT;
+
+ pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
+count, align);
+
+ if (!count)
+ return NULL;
+
+ mutex_lock(&cma_mutex);
+
+ pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count, 0, count,
+ (1 << align) - 1);
+ if (pageno >= cma->count) {
+ ret = -ENOMEM;
+ goto error;
+ }
+ bitmap_set(cma->bitmap, pageno, count);
+
+ pfn = cma->base_pfn + pageno;
+ ret = alloc_contig_range(pfn, pfn + count, 0, MIGRATE_CMA);
+ if (ret)
+ goto free;
+
If alloc_contig_range returns failure, the bitmap is still set. It will
never be freed so now the area cannot be used for CMA allocations any
more.
bitmap is cleared at the “free:” label.
+ mutex_unlock(&cma_mutex);
+
+ pr_debug("%s(): returned %p\n", __func__, pfn_to_page(pfn));
+ return pfn_to_page(pfn);
+free:
+ bitmap_clear(cma->bitmap, pageno, count);
+error:
+ mutex_unlock(&cma_mutex);
+ return NULL;
+}
+int dma_release_from_contiguous(struct device *dev, struct page *pages,
+ int count)
+{
+ struct cma *cma = get_dev_cma_area(dev);
+ unsigned long pfn;
+
+ if (!cma || !pages)
+ return 0;
+
+ pr_debug("%s(page %p)\n", __func__, (void *)pages);
+
+ pfn = page_to_pfn(pages);
+
+ if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
+ return 0;
+
+ mutex_lock(&cma_mutex);
+
+ bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count);
+ free_contig_pages(pfn, count);
+
+ mutex_unlock(&cma_mutex);
It feels like the mutex could be a lot lighter here. If the bitmap is
protected by a spinlock, it would only need to be held while the bitmap
was being cleared. free the contig pages outside the spinlock and clear
the bitmap afterwards.
It's not particularly important as the scalability of CMA is not
something to be concerned with at this point.
Mutex is used also to protect the core operations, ie. isolating pages
and such. This is because two CMA calls may want to work on the same
pageblock and we have to prevent that from happening.
We could add the spinlock for protecting the bitmap but we will still
need mutex for other uses.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz(o o)
ooo +--ooO--(_)--Ooo--
--
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Re: [PATCH 6/9] drivers: add Contiguous Memory Allocator
On Thu, Oct 06, 2011 at 03:54:46PM +0200, Marek Szyprowski wrote: > The Contiguous Memory Allocator is a set of helper functions for DMA > mapping framework that improves allocations of contiguous memory chunks. > > CMA grabs memory on system boot, marks it with CMA_MIGRATE_TYPE and > gives back to the system. Kernel is allowed to allocate movable pages > within CMA's managed memory so that it can be used for example for page > cache when DMA mapping do not use it. On dma_alloc_from_contiguous() > request such pages are migrated out of CMA area to free required > contiguous block and fulfill the request. This allows to allocate large > contiguous chunks of memory at any time assuming that there is enough > free memory available in the system. > > This code is heavily based on earlier works by Michal Nazarewicz. > > Signed-off-by: Marek Szyprowski > Signed-off-by: Kyungmin Park > CC: Michal Nazarewicz > --- > arch/Kconfig |3 + > drivers/base/Kconfig | 79 +++ > drivers/base/Makefile|1 + > drivers/base/dma-contiguous.c| 386 > ++ > include/asm-generic/dma-contiguous.h | 27 +++ > include/linux/device.h |4 + > include/linux/dma-contiguous.h | 106 ++ > 7 files changed, 606 insertions(+), 0 deletions(-) > create mode 100644 drivers/base/dma-contiguous.c > create mode 100644 include/asm-generic/dma-contiguous.h > create mode 100644 include/linux/dma-contiguous.h > > diff --git a/arch/Kconfig b/arch/Kconfig > index 4b0669c..a3b39a2 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -124,6 +124,9 @@ config HAVE_ARCH_TRACEHOOK > config HAVE_DMA_ATTRS > bool > > +config HAVE_DMA_CONTIGUOUS > + bool > + > config USE_GENERIC_SMP_HELPERS > bool > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > index 21cf46f..a5e6d75 100644 > --- a/drivers/base/Kconfig > +++ b/drivers/base/Kconfig > @@ -174,4 +174,83 @@ config SYS_HYPERVISOR > > source "drivers/base/regmap/Kconfig" > > +config CMA > + bool "Contiguous Memory Allocator (EXPERIMENTAL)" > + depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK && EXPERIMENTAL > + select MIGRATION > + select CMA_MIGRATE_TYPE > + help > + This enables the Contiguous Memory Allocator which allows drivers > + to allocate big physically-contiguous blocks of memory for use with > + hardware components that do not support I/O map nor scatter-gather. > + > + For more information see . > + If unsure, say "n". > + > +if CMA > + > +config CMA_DEBUG > + bool "CMA debug messages (DEVELOPEMENT)" s/DEVELOPEMENT/DEVELOPMENT/ Should it be under DEBUG_KERNEL? > + help > + Turns on debug messages in CMA. This produces KERN_DEBUG > + messages for every CMA call as well as various messages while > + processing calls such as dma_alloc_from_contiguous(). > + This option does not affect warning and error messages. > + > +comment "Default contiguous memory area size:" > + > +config CMA_SIZE_ABSOLUTE > + int "Absolute size (in MiB)" > + depends on !CMA_SIZE_SEL_PERCENTAGE > + default 16 > + help > + Defines the size (in MiB) of the default memory area for Contiguous > + Memory Allocator. > + > +config CMA_SIZE_PERCENTAGE > + int "Percentage of total memory" > + depends on !CMA_SIZE_SEL_ABSOLUTE > + default 10 > + help > + Defines the size of the default memory area for Contiguous Memory > + Allocator as a percentage of the total memory in the system. > + Why is this not a kernel parameter rather than a config option? Better yet, why do drivers not register how much CMA memory they are interested in and then the drive core figure out if it can allocate that much or not? > +choice > + prompt "Selected region size" > + default CMA_SIZE_SEL_ABSOLUTE > + > +config CMA_SIZE_SEL_ABSOLUTE > + bool "Use absolute value only" > + > +config CMA_SIZE_SEL_PERCENTAGE > + bool "Use percentage value only" > + > +config CMA_SIZE_SEL_MIN > + bool "Use lower value (minimum)" > + > +config CMA_SIZE_SEL_MAX > + bool "Use higher value (maximum)" > + > +endchoice > + > +config CMA_ALIGNMENT > + int "Maximum PAGE_SIZE order of alignment for contiguous buffers" > + range 4 9 > + default 8 > + help > + DMA mapping framework by default aligns all buffers to the smallest > + PAGE_SIZE order which is greater than or equal to the requested buffer > + size. This works well for buffers up to a few hundreds kilobytes, but > + for larger buffers it just a memory waste. With this parameter you can > + specify the maximum PAGE_SIZE order for contiguous buffers. Larger > + buffers will be aligned only to this specified order. The order is > + expressed as a power of two multiplied by the PAGE_SIZE. > + > + For example, if your s
Re: [PATCH 6/9] drivers: add Contiguous Memory Allocator
On Fri, Oct 14, 2011 at 04:57:30PM -0700, Andrew Morton wrote: > On Thu, 06 Oct 2011 15:54:46 +0200 > Marek Szyprowski wrote: > > +#ifdef phys_to_pfn > > +/* nothing to do */ > > +#elif defined __phys_to_pfn > > +# define phys_to_pfn __phys_to_pfn > > +#elif defined __va > > +# define phys_to_pfn(x) page_to_pfn(virt_to_page(__va(x))) > > +#else > > +# error phys_to_pfn implementation needed > > +#endif > > Yikes! > > This hackery should not be here, please. If we need a phys_to_pfn() > then let's write a proper one which lives in core MM and arch, then get > it suitably reviewed and integrated and then maintained. Another question is whether we have any arch where PFN != PHYS >> PAGE_SHIFT? We've used __phys_to_pfn() to implement that on ARM (with a corresponding __pfn_to_phys()). Catalin recently added a cast to __phys_to_pfn() for LPAE, which I don't think is required: -#define__phys_to_pfn(paddr)((paddr) >> PAGE_SHIFT) +#define__phys_to_pfn(paddr)((unsigned long)((paddr) >> PAGE_SHIFT)) since a phys_addr_t >> PAGE_SHIFT will be silently truncated if the passed in physical address was 64-bit anyway. (Note: we don't support > 32-bit PFNs). So, I'd suggest CMA should just use PFN_DOWN() and be done with it. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 6/9] drivers: add Contiguous Memory Allocator
On Thu, 06 Oct 2011 15:54:46 +0200
Marek Szyprowski wrote:
> The Contiguous Memory Allocator is a set of helper functions for DMA
> mapping framework that improves allocations of contiguous memory chunks.
>
> CMA grabs memory on system boot, marks it with CMA_MIGRATE_TYPE and
> gives back to the system. Kernel is allowed to allocate movable pages
> within CMA's managed memory so that it can be used for example for page
> cache when DMA mapping do not use it. On dma_alloc_from_contiguous()
> request such pages are migrated out of CMA area to free required
> contiguous block and fulfill the request. This allows to allocate large
> contiguous chunks of memory at any time assuming that there is enough
> free memory available in the system.
>
> This code is heavily based on earlier works by Michal Nazarewicz.
>
>
> ...
>
> +#ifdef phys_to_pfn
> +/* nothing to do */
> +#elif defined __phys_to_pfn
> +# define phys_to_pfn __phys_to_pfn
> +#elif defined __va
> +# define phys_to_pfn(x) page_to_pfn(virt_to_page(__va(x)))
> +#else
> +# error phys_to_pfn implementation needed
> +#endif
Yikes!
This hackery should not be here, please. If we need a phys_to_pfn()
then let's write a proper one which lives in core MM and arch, then get
it suitably reviewed and integrated and then maintained.
> +struct cma {
> + unsigned long base_pfn;
> + unsigned long count;
> + unsigned long *bitmap;
> +};
> +
> +struct cma *dma_contiguous_default_area;
> +
> +#ifndef CONFIG_CMA_SIZE_ABSOLUTE
> +#define CONFIG_CMA_SIZE_ABSOLUTE 0
> +#endif
> +
> +#ifndef CONFIG_CMA_SIZE_PERCENTAGE
> +#define CONFIG_CMA_SIZE_PERCENTAGE 0
> +#endif
No, .c files should not #define CONFIG_ variables like this.
One approach is
#ifdef CONFIG_FOO
#define BAR CONFIG_FOO
#else
#define BAR 0
#endif
but that's merely cosmetic fluff. A superior fix is to get the Kconfig
correct, so CONFIG_FOO cannot ever be undefined if we're compiling this
.c file.
> +static unsigned long size_abs = CONFIG_CMA_SIZE_ABSOLUTE * SZ_1M;
> +static unsigned long size_percent = CONFIG_CMA_SIZE_PERCENTAGE;
> +static long size_cmdline = -1;
Maybe a little documentation for these, explaining their role in
everything?
> +static int __init early_cma(char *p)
> +{
> + pr_debug("%s(%s)\n", __func__, p);
> + size_cmdline = memparse(p, &p);
> + return 0;
> +}
> +early_param("cma", early_cma);
Did this get added to Documentation/kernel-parameters.txt?
> +static unsigned long __init __cma_early_get_total_pages(void)
The leading __ seems unnecessay for a static function.
> +{
> + struct memblock_region *reg;
> + unsigned long total_pages = 0;
> +
> + /*
> + * We cannot use memblock_phys_mem_size() here, because
> + * memblock_analyze() has not been called yet.
> + */
> + for_each_memblock(memory, reg)
> + total_pages += memblock_region_memory_end_pfn(reg) -
> +memblock_region_memory_base_pfn(reg);
> + return total_pages;
> +}
> +
> +/**
> + * dma_contiguous_reserve() - reserve area for contiguous memory handling
> + *
> + * This funtion reserves memory from early allocator. It should be
> + * called by arch specific code once the early allocator (memblock or
> bootmem)
> + * has been activated and all other subsystems have already
> allocated/reserved
> + * memory.
> + */
Forgot to document the argument.
> +void __init dma_contiguous_reserve(phys_addr_t limit)
> +{
> + unsigned long selected_size = 0;
> + unsigned long total_pages;
> +
> + pr_debug("%s(limit %08lx)\n", __func__, (unsigned long)limit);
> +
> + total_pages = __cma_early_get_total_pages();
> + size_percent *= (total_pages << PAGE_SHIFT) / 100;
> +
> + pr_debug("%s: total available: %ld MiB, size absolute: %ld MiB, size
> percentage: %ld MiB\n",
> + __func__, (total_pages << PAGE_SHIFT) / SZ_1M,
> + size_abs / SZ_1M, size_percent / SZ_1M);
> +
> +#ifdef CONFIG_CMA_SIZE_SEL_ABSOLUTE
> + selected_size = size_abs;
> +#elif defined(CONFIG_CMA_SIZE_SEL_PERCENTAGE)
> + selected_size = size_percent;
> +#elif defined(CONFIG_CMA_SIZE_SEL_MIN)
> + selected_size = min(size_abs, size_percent);
> +#elif defined(CONFIG_CMA_SIZE_SEL_MAX)
> + selected_size = max(size_abs, size_percent);
> +#endif
geeze, what's all that stuff?
Whatever it's doing, it seems a bad idea to relegate these decisions to
Kconfig-time. The vast majority of users don't have control of their
kernel configuration! The code would be more flexible and generic if
this was done at runtime somehow.
> + if (size_cmdline != -1)
> + selected_size = size_cmdline;
> +
> + if (!selected_size)
> + return;
> +
> + pr_debug("%s: reserving %ld MiB for global area\n", __func__,
> + selected_size / SZ_1M);
> +
> + dma_declare_contiguous(NULL, selected_size, 0, limit);
> +};
> +
>
> ...
>
> +static struct cma *__cma_create_area(unsigned long base_pf
