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Add XBZRLE to ram_save_block and ram_save_live
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In the outgoing migration check to see if the page is cached and
changed, then send compressed page by using save_xbrle_page function.
In the incoming migration check to see if RAM_SAVE_FLAG_XBZRLE is set
and decompress the page (by using load_xbrle function).

Signed-off-by: Benoit Hudzia <benoit.hudzia@sap.com>
Signed-off-by: Petter Svard <petters@cs.umu.se>
Signed-off-by: Aidan Shribman <aidan.shribman@sap.com>
Signed-off-by: Orit Wasserman <owasserm@redhat.com>

Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
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@oritwas
oritwas authored and Juan Quintela committed Aug 8, 2012
1 parent 302dfbe commit 17ad9b3
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Showing 3 changed files with 184 additions and 2 deletions.
158 changes: 156 additions & 2 deletions arch_init.c
View file
Expand Up @@ -43,6 +43,7 @@
#include "hw/smbios.h"
#include "exec-memory.h"
#include "hw/pcspk.h"
#include "qemu/page_cache.h"

#ifdef DEBUG_ARCH_INIT
#define DPRINTF(fmt, ...) \
Expand Down Expand Up @@ -104,6 +105,7 @@ const uint32_t arch_type = QEMU_ARCH;
#define RAM_SAVE_FLAG_PAGE 0x08
#define RAM_SAVE_FLAG_EOS 0x10
#define RAM_SAVE_FLAG_CONTINUE 0x20
#define RAM_SAVE_FLAG_XBZRLE 0x40

#ifdef __ALTIVEC__
#include <altivec.h>
Expand Down Expand Up @@ -171,6 +173,24 @@ static int is_dup_page(uint8_t *page)
return 1;
}

/* struct contains XBZRLE cache and a static page
used by the compression */
static struct {
/* buffer used for XBZRLE encoding */
uint8_t *encoded_buf;
/* buffer for storing page content */
uint8_t *current_buf;
/* buffer used for XBZRLE decoding */
uint8_t *decoded_buf;
/* Cache for XBZRLE */
PageCache *cache;
} XBZRLE = {
.encoded_buf = NULL,
.current_buf = NULL,
.decoded_buf = NULL,
.cache = NULL,
};

static void save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
int cont, int flag)
{
Expand All @@ -183,6 +203,53 @@ static void save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,

}

#define ENCODING_FLAG_XBZRLE 0x1

static int save_xbzrle_page(QEMUFile *f, uint8_t *current_data,
ram_addr_t current_addr, RAMBlock *block,
ram_addr_t offset, int cont)
{
int encoded_len = 0, bytes_sent = -1;
uint8_t *prev_cached_page;

if (!cache_is_cached(XBZRLE.cache, current_addr)) {
cache_insert(XBZRLE.cache, current_addr,
g_memdup(current_data, TARGET_PAGE_SIZE));
return -1;
}

prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);

/* save current buffer into memory */
memcpy(XBZRLE.current_buf, current_data, TARGET_PAGE_SIZE);

/* XBZRLE encoding (if there is no overflow) */
encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
TARGET_PAGE_SIZE);
if (encoded_len == 0) {
DPRINTF("Skipping unmodified page\n");
return 0;
} else if (encoded_len == -1) {
DPRINTF("Overflow\n");
/* update data in the cache */
memcpy(prev_cached_page, current_data, TARGET_PAGE_SIZE);
return -1;
}

/* we need to update the data in the cache, in order to get the same data */
memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);

/* Send XBZRLE based compressed page */
save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_XBZRLE);
qemu_put_byte(f, ENCODING_FLAG_XBZRLE);
qemu_put_be16(f, encoded_len);
qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
bytes_sent = encoded_len + 1 + 2;

return bytes_sent;
}

static RAMBlock *last_block;
static ram_addr_t last_offset;

Expand All @@ -200,6 +267,7 @@ static int ram_save_block(QEMUFile *f)
ram_addr_t offset = last_offset;
int bytes_sent = -1;
MemoryRegion *mr;
ram_addr_t current_addr;

if (!block)
block = QLIST_FIRST(&ram_list.blocks);
Expand All @@ -220,13 +288,24 @@ static int ram_save_block(QEMUFile *f)
save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_COMPRESS);
qemu_put_byte(f, *p);
bytes_sent = 1;
} else {
} else if (migrate_use_xbzrle()) {
current_addr = block->offset + offset;
bytes_sent = save_xbzrle_page(f, p, current_addr, block,
offset, cont);
p = get_cached_data(XBZRLE.cache, current_addr);
}

/* either we didn't send yet (we may have had XBZRLE overflow) */
if (bytes_sent == -1) {
save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_PAGE);
qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
bytes_sent = TARGET_PAGE_SIZE;
}

break;
/* if page is unmodified, continue to the next */
if (bytes_sent != 0) {
break;
}
}

offset += TARGET_PAGE_SIZE;
Expand Down Expand Up @@ -304,6 +383,15 @@ static void sort_ram_list(void)
static void migration_end(void)
{
memory_global_dirty_log_stop();

if (migrate_use_xbzrle()) {
cache_fini(XBZRLE.cache);
g_free(XBZRLE.cache);
g_free(XBZRLE.encoded_buf);
g_free(XBZRLE.current_buf);
g_free(XBZRLE.decoded_buf);
XBZRLE.cache = NULL;
}
}

static void ram_migration_cancel(void *opaque)
Expand All @@ -323,6 +411,18 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
last_offset = 0;
sort_ram_list();

if (migrate_use_xbzrle()) {
XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
TARGET_PAGE_SIZE,
TARGET_PAGE_SIZE);
if (!XBZRLE.cache) {
DPRINTF("Error creating cache\n");
return -1;
}
XBZRLE.encoded_buf = g_malloc0(TARGET_PAGE_SIZE);
XBZRLE.current_buf = g_malloc(TARGET_PAGE_SIZE);
}

/* Make sure all dirty bits are set */
QLIST_FOREACH(block, &ram_list.blocks, next) {
for (addr = 0; addr < block->length; addr += TARGET_PAGE_SIZE) {
Expand Down Expand Up @@ -438,6 +538,47 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
return 0;
}

static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
{
int ret, rc = 0;
unsigned int xh_len;
int xh_flags;

if (!XBZRLE.decoded_buf) {
XBZRLE.decoded_buf = g_malloc(TARGET_PAGE_SIZE);
}

/* extract RLE header */
xh_flags = qemu_get_byte(f);
xh_len = qemu_get_be16(f);

if (xh_flags != ENCODING_FLAG_XBZRLE) {
fprintf(stderr, "Failed to load XBZRLE page - wrong compression!\n");
return -1;
}

if (xh_len > TARGET_PAGE_SIZE) {
fprintf(stderr, "Failed to load XBZRLE page - len overflow!\n");
return -1;
}
/* load data and decode */
qemu_get_buffer(f, XBZRLE.decoded_buf, xh_len);

/* decode RLE */
ret = xbzrle_decode_buffer(XBZRLE.decoded_buf, xh_len, host,
TARGET_PAGE_SIZE);
if (ret == -1) {
fprintf(stderr, "Failed to load XBZRLE page - decode error!\n");
rc = -1;
} else if (ret > TARGET_PAGE_SIZE) {
fprintf(stderr, "Failed to load XBZRLE page - size %d exceeds %d!\n",
ret, TARGET_PAGE_SIZE);
abort();
}

return rc;
}

static inline void *host_from_stream_offset(QEMUFile *f,
ram_addr_t offset,
int flags)
Expand Down Expand Up @@ -551,6 +692,19 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
}

qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
} else if (flags & RAM_SAVE_FLAG_XBZRLE) {
if (!migrate_use_xbzrle()) {
return -EINVAL;
}
void *host = host_from_stream_offset(f, addr, flags);
if (!host) {
return -EINVAL;
}

if (load_xbzrle(f, addr, host) < 0) {
ret = -EINVAL;
goto done;
}
}
error = qemu_file_get_error(f);
if (error) {
Expand Down
24 changes: 24 additions & 0 deletions migration.c
View file
Expand Up @@ -43,6 +43,9 @@ enum {

#define MAX_THROTTLE (32 << 20) /* Migration speed throttling */

/* Migration XBZRLE default cache size */
#define DEFAULT_MIGRATE_CACHE_SIZE (64 * 1024 * 1024)

static NotifierList migration_state_notifiers =
NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);

Expand All @@ -55,6 +58,7 @@ static MigrationState *migrate_get_current(void)
static MigrationState current_migration = {
.state = MIG_STATE_SETUP,
.bandwidth_limit = MAX_THROTTLE,
.xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE,
};

return &current_migration;
Expand Down Expand Up @@ -416,6 +420,7 @@ static MigrationState *migrate_init(const MigrationParams *params)
MigrationState *s = migrate_get_current();
int64_t bandwidth_limit = s->bandwidth_limit;
bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
int64_t xbzrle_cache_size = s->xbzrle_cache_size;

memcpy(enabled_capabilities, s->enabled_capabilities,
sizeof(enabled_capabilities));
Expand All @@ -425,6 +430,7 @@ static MigrationState *migrate_init(const MigrationParams *params)
s->params = *params;
memcpy(s->enabled_capabilities, enabled_capabilities,
sizeof(enabled_capabilities));
s->xbzrle_cache_size = xbzrle_cache_size;

s->bandwidth_limit = bandwidth_limit;
s->state = MIG_STATE_SETUP;
Expand Down Expand Up @@ -524,3 +530,21 @@ void qmp_migrate_set_downtime(double value, Error **errp)
value = MAX(0, MIN(UINT64_MAX, value));
max_downtime = (uint64_t)value;
}

int migrate_use_xbzrle(void)
{
MigrationState *s;

s = migrate_get_current();

return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
}

int64_t migrate_xbzrle_cache_size(void)
{
MigrationState *s;

s = migrate_get_current();

return s->xbzrle_cache_size;
}
4 changes: 4 additions & 0 deletions migration.h
View file
Expand Up @@ -41,6 +41,7 @@ struct MigrationState
MigrationParams params;
int64_t total_time;
bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
int64_t xbzrle_cache_size;
};

void process_incoming_migration(QEMUFile *f);
Expand Down Expand Up @@ -104,4 +105,7 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
uint8_t *dst, int dlen);
int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);

int migrate_use_xbzrle(void);
int64_t migrate_xbzrle_cache_size(void);

#endif

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