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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v5 09/13] xen: add cache coloring allocator for domains
This commit adds a new memory page allocator that implements the cache
coloring mechanism. The allocation algorithm enforces equal frequency
distribution of cache partitions, following the coloring configuration of a
domain. This allows an even utilization of cache sets for every domain.
Pages are stored in a color-indexed array of lists. Those lists are filled
by a simple init function which computes the color of each page.
When a domain requests a page, the allocator extract the page from the list
with the maximum number of free pages between those that the domain can
access, given its coloring configuration.
The allocator can only handle requests of order-0 pages. This allows for
easier implementation and since cache coloring targets only embedded systems,
it's assumed not to be a major problem.
The buddy allocator must coexist with the colored one because the Xen heap
isn't colored. For this reason a new Kconfig option and a command line
parameter are added to let the user set the amount of memory reserved for
the buddy allocator. Even when cache coloring is enabled, this memory
isn't managed by the colored allocator.
Colored heap information is dumped in the dump_heap() debug-key function.
Based on original work from: Luca Miccio <lucmiccio@xxxxxxxxx>
Signed-off-by: Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>
Signed-off-by: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
---
v5:
- Carlo Nonato as the new author
- the colored allocator balances color usage for each domain and it searches
linearly only in the number of colors (FIXME removed)
- addedd scrub functionality
- removed stub functions (still requires some macro definition)
- addr_to_color turned to mfn_to_color for easier operations
- removed BUG_ON in init_color_heap_pages() in favor of panic()
- only non empty page lists are logged in dump_color_heap()
v4:
- moved colored allocator code after buddy allocator because it now has
some dependencies on buddy functions
- buddy_alloc_size is now used only by the colored allocator
- fixed a bug that allowed the buddy to merge pages when they were colored
- free_color_heap_page() now calls mark_page_free()
- free_color_heap_page() uses of the frametable array for faster searches
- added FIXME comment for the linear search in free_color_heap_page()
- removed alloc_color_domheap_page() to let the colored allocator exploit
some more buddy allocator code
- alloc_color_heap_page() now allocs min address pages first
- reduced the mess in end_boot_allocator(): use the first loop for
init_color_heap_pages()
- fixed page_list_add_prev() (list.h) since it was doing the opposite of
what it was supposed to do
- fixed page_list_add_prev() (non list.h) to check also for next existence
- removed unused page_list_add_next()
- moved p2m code in another patch
---
docs/misc/arm/cache-coloring.rst | 37 ++++++
docs/misc/xen-command-line.pandoc | 14 +++
xen/arch/Kconfig | 12 ++
xen/arch/arm/include/asm/mm.h | 5 +
xen/arch/arm/llc-coloring.c | 13 ++
xen/common/page_alloc.c | 193 +++++++++++++++++++++++++++++-
xen/include/xen/llc-coloring.h | 4 +
7 files changed, 273 insertions(+), 5 deletions(-)
diff --git a/docs/misc/arm/cache-coloring.rst b/docs/misc/arm/cache-coloring.rst
index ae1dd8f4af..c5582340da 100644
--- a/docs/misc/arm/cache-coloring.rst
+++ b/docs/misc/arm/cache-coloring.rst
@@ -9,6 +9,9 @@ To compile LLC coloring support set ``CONFIG_LLC_COLORING=y``.
If needed, change the maximum number of colors with
``CONFIG_NR_LLC_COLORS=<n>``.
+If needed, change the buddy allocator reserved size with
+``CONFIG_BUDDY_ALLOCATOR_SIZE=<n>``.
+
Compile Xen and the toolstack and then configure it via
`Command line parameters`_. For DomUs follow `DomUs configuration`_.
@@ -86,6 +89,8 @@ More specific documentation is available at
`docs/misc/xen-command-line.pandoc`.
+----------------------+-------------------------------+
| ``dom0-llc-colors`` | Dom0 color configuration |
+----------------------+-------------------------------+
+| ``buddy-alloc-size`` | Buddy allocator reserved size |
++----------------------+-------------------------------+
Colors selection format
***********************
@@ -160,6 +165,17 @@ DomUs colors can be set via Device Tree, also for Dom0less
configurations
**Note:** If no color configuration is provided for a domain, the default one,
which corresponds to all available colors, is used instead.
+Colored allocator and buddy allocator
+*************************************
+
+The colored allocator distributes pages based on color configurations of
+domains so that each domains only gets pages of its own colors.
+The colored allocator is meant as an alternative to the buddy allocator because
+its allocation policy is by definition incompatible with the generic one. Since
+the Xen heap is not colored yet, we need to support the coexistence of the two
+allocators and some memory must be left for the buddy one. Buddy memory
+reservation is configured via Kconfig or via command-line.
+
Known issues and limitations
****************************
@@ -170,3 +186,24 @@ In the domain configuration, "xen,static-mem" allows
memory to be statically
allocated to the domain. This isn't possibile when LLC coloring is enabled,
because that memory can't be guaranteed to use only colors assigned to the
domain.
+
+Cache coloring is intended only for embedded systems
+####################################################
+
+The current implementation aims to satisfy the need of predictability in
+embedded systems with small amount of memory to be managed in a colored way.
+Given that, some shortcuts are taken in the development. Expect worse
+performances on larger systems.
+
+Colored allocator can only make use of order-0 pages
+####################################################
+
+The cache coloring technique relies on memory mappings and on the smallest
+amount of memory that can be mapped to achieve the maximum number of colors
+(cache partitions) possible. This amount is what is normally called a page and,
+in Xen terminology, the order-0 page is the smallest one. The fairly simple
+colored allocator currently implemented, makes use only of such pages.
+It must be said that a more complex one could, in theory, adopt higher order
+pages if the colors selection contained adjacent colors. Two subsequent colors,
+for example, can be represented by an order-1 page, four colors correspond to
+an order-2 page, etc.
diff --git a/docs/misc/xen-command-line.pandoc
b/docs/misc/xen-command-line.pandoc
index 51f6adf035..163fe7bcb1 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -270,6 +270,20 @@ and not running softirqs. Reduce this if softirqs are not
being run frequently
enough. Setting this to a high value may cause boot failure, particularly if
the NMI watchdog is also enabled.
+### buddy-alloc-size (arm64)
+> `= <size>`
+
+> Default: `64M`
+
+Amount of memory reserved for the buddy allocator when colored allocator is
+active. This options is parsed only when LLC coloring support is enabled.
+The colored allocator is meant as an alternative to the buddy allocator,
+because its allocation policy is by definition incompatible with the generic
+one. Since the Xen heap systems is not colored yet, we need to support the
+coexistence of the two allocators for now. This parameter, which is optional
+and for expert only, it's used to set the amount of memory reserved to the
+buddy allocator.
+
### cet
= List of [ shstk=<bool>, ibt=<bool> ]
diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig
index aad7e9da38..f4c1406c02 100644
--- a/xen/arch/Kconfig
+++ b/xen/arch/Kconfig
@@ -47,3 +47,15 @@ config NR_LLC_COLORS
bound. The runtime value is autocomputed or manually set via cmdline.
The default value corresponds to an 8 MiB 16-ways LLC, which should be
more than what needed in the general case.
+
+config BUDDY_ALLOCATOR_SIZE
+ int "Buddy allocator reserved memory size (MiB)"
+ default "64"
+ depends on LLC_COLORING
+ help
+ Amount of memory reserved for the buddy allocator to work alongside
+ the colored one. The colored allocator is meant as an alternative to
+ the buddy allocator because its allocation policy is by definition
+ incompatible with the generic one. Since the Xen heap is not colored
+ yet, we need to support the coexistence of the two allocators and some
+ memory must be left for the buddy one.
diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
index cbcf3bf147..1829c559d6 100644
--- a/xen/arch/arm/include/asm/mm.h
+++ b/xen/arch/arm/include/asm/mm.h
@@ -145,6 +145,11 @@ struct page_info
#else
#define PGC_static 0
#endif
+#ifdef CONFIG_LLC_COLORING
+/* Page is cache colored */
+#define _PGC_colored PG_shift(4)
+#define PGC_colored PG_mask(1, 4)
+#endif
/* ... */
/* Page is broken? */
#define _PGC_broken PG_shift(7)
diff --git a/xen/arch/arm/llc-coloring.c b/xen/arch/arm/llc-coloring.c
index d3de5f14cb..526129cc43 100644
--- a/xen/arch/arm/llc-coloring.c
+++ b/xen/arch/arm/llc-coloring.c
@@ -30,6 +30,9 @@ static unsigned int __ro_after_init nr_colors =
CONFIG_NR_LLC_COLORS;
static unsigned int __ro_after_init dom0_colors[CONFIG_NR_LLC_COLORS];
static unsigned int __ro_after_init dom0_num_colors;
+#define mfn_color_mask (nr_colors - 1)
+#define mfn_to_color(mfn) (mfn_x(mfn) & mfn_color_mask)
+
/*
* Parse the coloring configuration given in the buf string, following the
* syntax below.
@@ -312,6 +315,16 @@ int domain_set_llc_colors_from_str(struct domain *d, const
char *str)
return domain_check_colors(d);
}
+unsigned int page_to_llc_color(const struct page_info *pg)
+{
+ return mfn_to_color(page_to_mfn(pg));
+}
+
+unsigned int get_nr_llc_colors(void)
+{
+ return nr_colors;
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 3bf3120287..54f52e8677 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -126,6 +126,7 @@
#include <xen/irq.h>
#include <xen/keyhandler.h>
#include <xen/lib.h>
+#include <xen/llc-coloring.h>
#include <xen/mm.h>
#include <xen/nodemask.h>
#include <xen/numa.h>
@@ -158,7 +159,11 @@
#define PGC_static 0
#endif
-#define preserved_flags (PGC_extra | PGC_static)
+#ifndef PGC_colored
+#define PGC_colored 0
+#endif
+
+#define preserved_flags (PGC_extra | PGC_static | PGC_colored)
#ifndef PGT_TYPE_INFO_INITIALIZER
#define PGT_TYPE_INFO_INITIALIZER 0
@@ -1946,6 +1951,162 @@ static unsigned long avail_heap_pages(
return free_pages;
}
+/*************************
+ * COLORED SIDE-ALLOCATOR
+ *
+ * Pages are grouped by LLC color in lists which are globally referred to as
the
+ * color heap. Lists are populated in end_boot_allocator().
+ * After initialization there will be N lists where N is the number of
+ * available colors on the platform.
+ */
+static struct page_list_head *__ro_after_init _color_heap;
+static unsigned long *__ro_after_init free_colored_pages;
+
+/* Memory required for buddy allocator to work with colored one */
+#ifdef CONFIG_LLC_COLORING
+static unsigned long __initdata buddy_alloc_size =
+ MB(CONFIG_BUDDY_ALLOCATOR_SIZE);
+size_param("buddy-alloc-size", buddy_alloc_size);
+
+#define domain_num_llc_colors(d) ((d)->num_llc_colors)
+#define domain_llc_color(d, i) ((d)->llc_colors[(i)])
+#else
+static unsigned long __initdata buddy_alloc_size;
+
+#define domain_num_llc_colors(d) 0
+#define domain_llc_color(d, i) 0
+#define page_to_llc_color(p) 0
+#define get_nr_llc_colors() 0
+#endif
+
+#define color_heap(color) (&_color_heap[color])
+
+void free_color_heap_page(struct page_info *pg, bool need_scrub)
+{
+ unsigned int color = page_to_llc_color(pg);
+ struct page_list_head *head = color_heap(color);
+
+ spin_lock(&heap_lock);
+
+ mark_page_free(pg, page_to_mfn(pg));
+
+ if ( need_scrub )
+ {
+ pg->count_info |= PGC_need_scrub;
+ poison_one_page(pg);
+ }
+
+ pg->count_info |= PGC_colored;
+ free_colored_pages[color]++;
+ page_list_add(pg, head);
+
+ spin_unlock(&heap_lock);
+}
+
+struct page_info *alloc_color_heap_page(unsigned int memflags, struct domain
*d)
+{
+ struct page_info *pg = NULL;
+ unsigned int i, color;
+ unsigned long max = 0;
+ bool need_tlbflush = false;
+ uint32_t tlbflush_timestamp = 0;
+ bool scrub = !(memflags & MEMF_no_scrub);
+
+ spin_lock(&heap_lock);
+
+ for ( i = 0; i < domain_num_llc_colors(d); i++ )
+ {
+ unsigned long free = free_colored_pages[domain_llc_color(d, i)];
+
+ if ( free > max )
+ {
+ color = domain_llc_color(d, i);
+ pg = page_list_first(color_heap(color));
+ max = free;
+ }
+ }
+
+ if ( !pg )
+ {
+ spin_unlock(&heap_lock);
+ return NULL;
+ }
+
+ pg->count_info = PGC_state_inuse | PGC_colored |
+ (pg->count_info & PGC_need_scrub);
+ free_colored_pages[color]--;
+ page_list_del(pg, color_heap(color));
+
+ if ( !(memflags & MEMF_no_tlbflush) )
+ accumulate_tlbflush(&need_tlbflush, pg, &tlbflush_timestamp);
+
+ init_free_page_fields(pg);
+
+ spin_unlock(&heap_lock);
+
+ if ( test_and_clear_bit(_PGC_need_scrub, &pg->count_info) && scrub )
+ scrub_one_page(pg);
+ else if ( scrub )
+ check_one_page(pg);
+
+ if ( need_tlbflush )
+ filtered_flush_tlb_mask(tlbflush_timestamp);
+
+ flush_page_to_ram(mfn_x(page_to_mfn(pg)),
+ !(memflags & MEMF_no_icache_flush));
+
+ return pg;
+}
+
+void __init init_color_heap_pages(struct page_info *pg, unsigned long nr_pages)
+{
+ unsigned int i;
+ bool need_scrub = (system_state < SYS_STATE_active &&
+ opt_bootscrub == BOOTSCRUB_IDLE);
+
+ if ( buddy_alloc_size )
+ {
+ unsigned long buddy_pages = min(PFN_DOWN(buddy_alloc_size), nr_pages);
+
+ init_heap_pages(pg, buddy_pages);
+ nr_pages -= buddy_pages;
+ buddy_alloc_size -= buddy_pages << PAGE_SHIFT;
+ pg += buddy_pages;
+ }
+
+ if ( !_color_heap )
+ {
+ unsigned int nr_colors = get_nr_llc_colors();
+
+ _color_heap = xmalloc_array(struct page_list_head, nr_colors);
+ free_colored_pages = xzalloc_array(unsigned long, nr_colors);
+ if ( !_color_heap || !free_colored_pages )
+ panic("Can't allocate colored heap. Buddy reserved size is too
low");
+
+ for ( i = 0; i < nr_colors; i++ )
+ INIT_PAGE_LIST_HEAD(color_heap(i));
+ }
+
+ if ( nr_pages )
+ printk(XENLOG_DEBUG
+ "Init color heap with %lu pages starting from: %#"PRIx64"\n",
+ nr_pages, page_to_maddr(pg));
+
+ for ( i = 0; i < nr_pages; i++ )
+ free_color_heap_page(&pg[i], need_scrub);
+}
+
+void dump_color_heap(void)
+{
+ unsigned int color;
+
+ printk("Dumping color heap info\n");
+ for ( color = 0; color < get_nr_llc_colors(); color++ )
+ if ( free_colored_pages[color] > 0 )
+ printk("Color heap[%u]: %lu pages\n",
+ color, free_colored_pages[color]);
+}
+
void __init end_boot_allocator(void)
{
unsigned int i;
@@ -1965,7 +2126,13 @@ void __init end_boot_allocator(void)
for ( i = nr_bootmem_regions; i-- > 0; )
{
struct bootmem_region *r = &bootmem_region_list[i];
- if ( r->s < r->e )
+
+ if ( r->s >= r->e )
+ continue;
+
+ if ( llc_coloring_enabled )
+ init_color_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s);
+ else
init_heap_pages(mfn_to_page(_mfn(r->s)), r->e - r->s);
}
nr_bootmem_regions = 0;
@@ -2461,7 +2628,14 @@ struct page_info *alloc_domheap_pages(
if ( memflags & MEMF_no_owner )
memflags |= MEMF_no_refcount;
- if ( !dma_bitsize )
+ /* Only domains are supported for coloring */
+ if ( d && is_domain_llc_colored(d) )
+ {
+ /* Colored allocation must be done on 0 order */
+ if ( order || (pg = alloc_color_heap_page(memflags, d)) == NULL )
+ return NULL;
+ }
+ else if ( !dma_bitsize )
memflags &= ~MEMF_no_dma;
else if ( (dma_zone = bits_to_zone(dma_bitsize)) < zone_hi )
pg = alloc_heap_pages(dma_zone + 1, zone_hi, order, memflags, d);
@@ -2486,7 +2660,10 @@ struct page_info *alloc_domheap_pages(
}
if ( assign_page(pg, order, d, memflags) )
{
- free_heap_pages(pg, order, memflags & MEMF_no_scrub);
+ if ( pg->count_info & PGC_colored )
+ free_color_heap_page(pg, memflags & MEMF_no_scrub);
+ else
+ free_heap_pages(pg, order, memflags & MEMF_no_scrub);
return NULL;
}
}
@@ -2569,7 +2746,10 @@ void free_domheap_pages(struct page_info *pg, unsigned
int order)
scrub = 1;
}
- free_heap_pages(pg, order, scrub);
+ if ( pg->count_info & PGC_colored )
+ free_color_heap_page(pg, scrub);
+ else
+ free_heap_pages(pg, order, scrub);
}
if ( drop_dom_ref )
@@ -2676,6 +2856,9 @@ static void cf_check dump_heap(unsigned char key)
continue;
printk("Node %d has %lu unscrubbed pages\n", i, node_need_scrub[i]);
}
+
+ if ( llc_coloring_enabled )
+ dump_color_heap();
}
static __init int cf_check register_heap_trigger(void)
diff --git a/xen/include/xen/llc-coloring.h b/xen/include/xen/llc-coloring.h
index fa2edc8ad8..7cd481e955 100644
--- a/xen/include/xen/llc-coloring.h
+++ b/xen/include/xen/llc-coloring.h
@@ -36,6 +36,10 @@ void domain_dump_llc_colors(struct domain *d);
int domain_set_llc_colors_domctl(struct domain *d,
const struct xen_domctl_set_llc_colors
*config);
+struct page_info;
+unsigned int page_to_llc_color(const struct page_info *pg);
+unsigned int get_nr_llc_colors(void);
+
#endif /* __COLORING_H__ */
/*
--
2.34.1
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