@@ -88,6 +88,20 @@
early region and the framework will handle the rest
including choosing the right early allocator.
+ 4. CMA allows a run-time configuration of the memory regions it
+ will use to allocate chunks of memory from. The set of memory
+ regions is given on command line so it can be easily changed
+ without the need for recompiling the kernel.
+
+ Each region has it's own size, alignment demand, a start
+ address (physical address where it should be placed) and an
+ allocator algorithm assigned to the region.
+
+ This means that there can be different algorithms running at
+ the same time, if different devices on the platform have
+ distinct memory usage characteristics and different algorithm
+ match those the best way.
+
** Use cases
Let's analyse some imaginary system that uses the CMA to see how
@@ -162,7 +176,6 @@
This solution also shows how with CMA you can assign private pools
of memory to each device if that is required.
-
Allocation mechanisms can be replaced dynamically in a similar
manner as well. Let's say that during testing, it has been
discovered that, for a given shared region of 40 MiB,
@@ -217,6 +230,42 @@
it will be set to a PAGE_SIZE. start will be aligned to
alignment.
+ If command line parameter support is enabled, this attribute can
+ also be overriden by a command line "cma" parameter. When given
+ on command line its forrmat is as follows:
+
+ regions-attr ::= [ regions [ ';' ] ]
+ regions ::= region [ ';' regions ]
+
+ region ::= REG-NAME
+ '=' size
+ [ '@' start ]
+ [ '/' alignment ]
+ [ ':' ALLOC-NAME ]
+
+ size ::= MEMSIZE // size of the region
+ start ::= MEMSIZE // desired start address of
+ // the region
+ alignment ::= MEMSIZE // alignment of the start
+ // address of the region
+
+ REG-NAME specifies the name of the region. All regions given at
+ via the regions attribute need to have a name. Moreover, all
+ regions need to have a unique name. If two regions have the same
+ name it is unspecified which will be used when requesting to
+ allocate memory from region with given name.
+
+ ALLOC-NAME specifies the name of allocator to be used with the
+ region. If no allocator name is provided, the "default"
+ allocator will be used with the region. The "default" allocator
+ is, of course, the first allocator that has been registered. ;)
+
+ size, start and alignment are specified in bytes with suffixes
+ that memparse() accept. If start is given, the region will be
+ reserved on given starting address (or at close to it as
+ possible). If alignment is specified, the region will be aligned
+ to given value.
+
**** Map
The format of the "map" attribute is as follows:
@@ -260,8 +309,33 @@
SysFS and can be changed at run-time by writing to
/sys/kernel/mm/contiguous/map.
+ If command line parameter support is enabled, this attribute can
+ also be overriden by a command line "cma.map" parameter.
+
+**** Examples
+
Some examples (whitespace added for better readability):
+ cma = r1 = 64M // 64M region
+ @512M // starting at address 512M
+ // (or at least as near as possible)
+ /1M // make sure it's aligned to 1M
+ :foo(bar); // uses allocator "foo" with "bar"
+ // as parameters for it
+ r2 = 64M // 64M region
+ /1M; // make sure it's aligned to 1M
+ // uses the first available allocator
+ r3 = 64M // 64M region
+ @512M // starting at address 512M
+ :foo; // uses allocator "foo" with no parameters
+
+ cma_map = foo = r1;
+ // device foo with kind==NULL uses region r1
+
+ foo/quaz = r2; // OR:
+ /quaz = r2;
+ // device foo with kind == "quaz" uses region r2
+
cma_map = foo/quaz = r1;
// device foo with type == "quaz" uses region r1
@@ -529,10 +603,11 @@
int cma_set_defaults(struct cma_region *regions, const char *map)
- It needs to be called prior to reserving regions. It let one
- specify the list of regions defined by platform and the map
- attribute. The map may point to a string in __initdata. See
- above in this document for example usage of this function.
+ It needs to be called after early params have been parsed but
+ prior to reserving regions. It let one specify the list of
+ regions defined by platform and the map attribute. The map may
+ point to a string in __initdata. See above in this document for
+ example usage of this function.
** Future work
@@ -43,6 +43,7 @@ parameter is applicable:
AVR32 AVR32 architecture is enabled.
AX25 Appropriate AX.25 support is enabled.
BLACKFIN Blackfin architecture is enabled.
+ CMA Contiguous Memory Allocator is enabled.
EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
EFI EFI Partitioning (GPT) is enabled
EIDE EIDE/ATAPI support is enabled.
@@ -478,6 +479,12 @@ and is between 256 and 4096 characters. It is defined in the file
Also note the kernel might malfunction if you disable
some critical bits.
+ cma= [CMA] List of CMA regions.
+ See Documentation/contiguous-memory.txt for details.
+
+ cma.map= [CMA] CMA mapping
+ See Documentation/contiguous-memory.txt for details.
+
cmo_free_hint= [PPC] Format: { yes | no }
Specify whether pages are marked as being inactive
when they are freed. This is used in CMO environments
@@ -353,6 +353,15 @@ config CMA_SYSFS
<Documentation/contiguous-memory.txt> and
<Documentation/ABI/testing/sysfs-kernel-mm-contiguous> files.
+config CMA_CMDLINE
+ bool "CMA command line parameters support"
+ depends on CMA_DEVELOPEMENT
+ help
+ Enable support for cma and cma.map command line parameters.
+ This lets overwrite the CMA defaults defined by for the
+ platform. This should only be usable during development and
+ testing.
+
config CMA_BEST_FIT
bool "CMA best-fit allocator"
depends on CMA
@@ -103,6 +103,12 @@ static int __init cma_map_param(char *param)
return 0;
}
+#if defined CONFIG_CMA_CMDLINE
+
+early_param("cma.map", cma_map_param);
+
+#endif
+
/************************* Early regions *************************/
@@ -110,6 +116,125 @@ static int __init cma_map_param(char *param)
struct list_head cma_early_regions __initdata =
LIST_HEAD_INIT(cma_early_regions);
+#ifdef CONFIG_CMA_CMDLINE
+
+/*
+ * regions-attr ::= [ regions [ ';' ] ]
+ * regions ::= region [ ';' regions ]
+ *
+ * region ::= [ '-' ] reg-name
+ * '=' size
+ * [ '@' start ]
+ * [ '/' alignment ]
+ * [ ':' alloc-name ]
+ *
+ * See Documentation/contiguous-memory.txt for details.
+ *
+ * Example:
+ * cma=reg1=64M:bf;reg2=32M@0x100000:bf;reg3=64M/1M:bf
+ *
+ * If allocator is ommited the first available allocater will be used.
+ */
+
+#define NUMPARSE(cond_ch, type, cond) ({ \
+ unsigned long long v = 0; \
+ if (*param == (cond_ch)) { \
+ const char *const msg = param + 1; \
+ v = memparse(msg, ¶m); \
+ if (!v || v > ~(type)0 || !(cond)) { \
+ pr_err("param: invalid value near %s\n", msg); \
+ ret = -EINVAL; \
+ break; \
+ } \
+ } \
+ v; \
+ })
+
+static int __init cma_param_parse(char *param)
+{
+ static struct cma_region regions[16];
+
+ size_t left = ARRAY_SIZE(regions);
+ struct cma_region *reg = regions;
+ int ret = 0;
+
+ pr_debug("param: %s\n", param);
+
+ for (; *param; ++reg) {
+ dma_addr_t start, alignment;
+ size_t size;
+
+ if (unlikely(!--left)) {
+ pr_err("param: too many early regions\n");
+ return -ENOSPC;
+ }
+
+ /* Parse name */
+ reg->name = param;
+ param = strchr(param, '=');
+ if (!param || param == reg->name) {
+ pr_err("param: expected \"<name>=\" near %s\n",
+ reg->name);
+ ret = -EINVAL;
+ break;
+ }
+ *param = '\0';
+
+ /* Parse numbers */
+ size = NUMPARSE('\0', size_t, true);
+ start = NUMPARSE('@', dma_addr_t, true);
+ alignment = NUMPARSE('/', dma_addr_t, (v & (v - 1)) == 0);
+
+ alignment = max(alignment, (dma_addr_t)PAGE_SIZE);
+ start = ALIGN(start, alignment);
+ size = PAGE_ALIGN(size);
+ if (start + size < start) {
+ pr_err("param: invalid start, size combination\n");
+ ret = -EINVAL;
+ break;
+ }
+
+ /* Parse allocator */
+ if (*param == ':') {
+ reg->alloc_name = ++param;
+ while (*param && *param != ';')
+ ++param;
+ if (param == reg->alloc_name)
+ reg->alloc_name = NULL;
+ }
+
+ /* Go to next */
+ if (*param == ';') {
+ *param = '\0';
+ ++param;
+ } else if (*param) {
+ pr_err("param: expecting ';' or end of parameter near %s\n",
+ param);
+ ret = -EINVAL;
+ break;
+ }
+
+ /* Add */
+ reg->size = size;
+ reg->start = start;
+ reg->alignment = alignment;
+ reg->copy_name = 1;
+
+ list_add_tail(®->list, &cma_early_regions);
+
+ pr_debug("param: registering early region %s (%p@%p/%p)\n",
+ reg->name, (void *)reg->size, (void *)reg->start,
+ (void *)reg->alignment);
+ }
+
+ return ret;
+}
+early_param("cma", cma_param_parse);
+
+#undef NUMPARSE
+
+#endif
+
int __init __must_check cma_early_region_register(struct cma_region *reg)
{