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migration: Fix calculation of bytes_transferred 

When a page with all identical bytes is transferred, it is counted
as a full page (TARGET_PAGE_SIZE) although only one byte is actually
sent. Fix this by changing ram_save_block() to return the number of
bytes sent instead of a boolean value. This makes bandwidth
estimation, and consequently downtime estimation, more precise.

Signed-off-by: Pierre Riteau <Pierre.Riteau@irisa.fr>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Pierre Riteau 2010-05-12 15:12:44 +02:00 committed by Anthony Liguori
parent a132a679c3
commit 3fc250b4be
1 changed files with 12 additions and 9 deletions
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21
arch_init.c
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@ -108,7 +108,7 @@ static int ram_save_block(QEMUFile *f)
static ram_addr_t current_addr = 0;
ram_addr_t saved_addr = current_addr;
ram_addr_t addr = 0;
int found = 0;
int bytes_sent = 0;
while (addr < last_ram_offset) {
if (cpu_physical_memory_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
@ -123,19 +123,20 @@ static int ram_save_block(QEMUFile *f)
if (is_dup_page(p, *p)) {
qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
qemu_put_byte(f, *p);
bytes_sent = 1;
} else {
qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
bytes_sent = TARGET_PAGE_SIZE;
}
found = 1;
break;
}
addr += TARGET_PAGE_SIZE;
current_addr = (saved_addr + addr) % last_ram_offset;
}
return found;
return bytes_sent;
}
static uint64_t bytes_transferred;
@ -206,11 +207,11 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
bwidth = qemu_get_clock_ns(rt_clock);
while (!qemu_file_rate_limit(f)) {
int ret;
int bytes_sent;
ret = ram_save_block(f);
bytes_transferred += ret * TARGET_PAGE_SIZE;
if (ret == 0) { /* no more blocks */
bytes_sent = ram_save_block(f);
bytes_transferred += bytes_sent;
if (bytes_sent == 0) { /* no more blocks */
break;
}
}
@ -226,9 +227,11 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
/* try transferring iterative blocks of memory */
if (stage == 3) {
int bytes_sent;
/* flush all remaining blocks regardless of rate limiting */
while (ram_save_block(f) != 0) {
bytes_transferred += TARGET_PAGE_SIZE;
while ((bytes_sent = ram_save_block(f)) != 0) {
bytes_transferred += bytes_sent;
}
cpu_physical_memory_set_dirty_tracking(0);
}