[PATCH 4/5] Separate migration dirty bitmap

Umesh Deshpande
2011-08-27T18:09:47Z

This patch creates a migration bitmap, which is periodically kept in sync with
the qemu bitmap. A separate copy of the dirty bitmap for the migration avoids
concurrent access to the qemu bitmap from the iothread and the migration thread.

Signed-off-by: Umesh Deshpande <udeshpan@redhat.com>
---
arch_init.c | 17 ++++++++---------
cpu-all.h | 37 +++++++++++++++++++++++++++++++++++++
exec.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 102 insertions(+), 9 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 9d02270..b5b852b 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -124,13 +124,13 @@ static int ram_save_block(QEMUFile *f)
current_addr = block->offset + offset;

do {
- if (cpu_physical_memory_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
+ if (migration_bitmap_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
uint8_t *p;
int cont = (block == last_block) ? RAM_SAVE_FLAG_CONTINUE : 0;

- cpu_physical_memory_reset_dirty(current_addr,
- current_addr + TARGET_PAGE_SIZE,
- MIGRATION_DIRTY_FLAG);
+ migration_bitmap_reset_dirty(current_addr,
+ current_addr + TARGET_PAGE_SIZE,
+ MIGRATION_DIRTY_FLAG);

p = block->host + offset;

@@ -187,7 +187,7 @@ static ram_addr_t ram_save_remaining(void)
ram_addr_t addr;
for (addr = block->offset; addr < block->offset + block->length;
addr += TARGET_PAGE_SIZE) {
- if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
+ if (migration_bitmap_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
count++;
}
}
@@ -267,6 +267,8 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
return 0;
}

+ sync_migration_bitmap(0, TARGET_PHYS_ADDR_MAX);
+
if (stage == 1) {
RAMBlock *block;
bytes_transferred = 0;
@@ -279,10 +281,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
QLIST_FOREACH(block, &ram_list.blocks, next) {
for (addr = block->offset; addr < block->offset + block->length;
addr += TARGET_PAGE_SIZE) {
- if (!cpu_physical_memory_get_dirty(addr,
- MIGRATION_DIRTY_FLAG)) {
- cpu_physical_memory_set_dirty(addr);
- }
+ migration_bitmap_set_dirty(addr);
}
}

diff --git a/cpu-all.h b/cpu-all.h
index b85483f..8181f8b 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -935,6 +935,7 @@ typedef struct RAMBlock {
typedef struct RAMList {
QemuMutex mutex; /* Protects RAM block list */
uint8_t *phys_dirty;
+ uint8_t *migration_bitmap; /* Dedicated bitmap for migration thread */
uint32_t version; /* To detect ram block addition/removal */
QLIST_HEAD(ram, RAMBlock) blocks;
QLIST_HEAD(, RAMBlock) blocks_mru;
@@ -1009,8 +1010,44 @@ static inline void cpu_physical_memory_mask_dirty_range(ram_addr_t start,
}
}

+
+
void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t end,
int dirty_flags);
+
+static inline int migration_bitmap_get_dirty(ram_addr_t addr,
+ int dirty_flags)
+{
+ return ram_list.migration_bitmap[addr >> TARGET_PAGE_BITS] & dirty_flags;
+}
+
+static inline void migration_bitmap_set_dirty(ram_addr_t addr)
+{
+ ram_list.migration_bitmap[addr >> TARGET_PAGE_BITS] = 0xff;
+}
+
+static inline void migration_bitmap_mask_dirty_range(ram_addr_t start,
+ int length,
+ int dirty_flags)
+{
+ int i, mask, len;
+ uint8_t *p;
+
+ len = length >> TARGET_PAGE_BITS;
+ mask = ~dirty_flags;
+ p = ram_list.migration_bitmap + (start >> TARGET_PAGE_BITS);
+ for (i = 0; i < len; i++) {
+ p[i] &= mask;
+ }
+}
+
+
+void migration_bitmap_reset_dirty(ram_addr_t start,
+ ram_addr_t end,
+ int dirty_flags);
+
+void sync_migration_bitmap(ram_addr_t start, ram_addr_t end);
+
void cpu_tlb_update_dirty(CPUState *env);

int cpu_physical_memory_set_dirty_tracking(int enable);
diff --git a/exec.c b/exec.c
index 7627483..8dfbdbc 100644
--- a/exec.c
+++ b/exec.c
@@ -2111,6 +2111,10 @@ void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t end,
abort();
}

+ if (kvm_enabled()) {
+ return;
+ }
+
for(env = first_cpu; env != NULL; env = env->next_cpu) {
int mmu_idx;
for (mmu_idx = 0; mmu_idx < NB_MMU_MODES; mmu_idx++) {
@@ -2119,8 +2123,54 @@ void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t end,
start1, length);
}
}
+
+}
+
+void migration_bitmap_reset_dirty(ram_addr_t start, ram_addr_t end,
+ int dirty_flags)
+{
+ unsigned long length;
+
+ start &= TARGET_PAGE_MASK;
+ end = TARGET_PAGE_ALIGN(end);
+
+ length = end - start;
+ if (length == 0) {
+ return;
+ }
+
+ migration_bitmap_mask_dirty_range(start, length, dirty_flags);
+}
+
+/* Synchronizes migration bitmap with the qemu dirty bitmap.
+ * Called by acquiring the iothread mutex */
+
+void sync_migration_bitmap(ram_addr_t start, ram_addr_t end)
+{
+ unsigned long length, len, i;
+ ram_addr_t addr;
+ start &= TARGET_PAGE_MASK;
+ end = TARGET_PAGE_ALIGN(end);
+
+ length = end - start;
+ if (length == 0) {
+ return;
+ }
+
+ len = length >> TARGET_PAGE_BITS;
+ for (i = 0; i < len; i++) {
+ addr = i << TARGET_PAGE_BITS;
+ if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
+ migration_bitmap_set_dirty(addr);
+ cpu_physical_memory_reset_dirty(addr, addr + TARGET_PAGE_SIZE,
+ MIGRATION_DIRTY_FLAG);
+ }
+ }
+
}

+
+
int cpu_physical_memory_set_dirty_tracking(int enable)
{
int ret = 0;
@@ -2999,6 +3049,13 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
memset(ram_list.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS),
0xff, size >> TARGET_PAGE_BITS);

+ ram_list.migration_bitmap = qemu_realloc(ram_list.phys_dirty,
+ last_ram_offset() >>
+ TARGET_PAGE_BITS);
+
+ memset(ram_list.migration_bitmap + (new_block->offset >> TARGET_PAGE_BITS),
+ 0xff, size >> TARGET_PAGE_BITS);
+
qemu_mutex_unlock_migrate_ram();

if (kvm_enabled())
--
1.7.4.1