Re: [RFC PATCH 5/6] savevm: Migrate RAM based on name/offset

Anthony Liguori
2010-06-08T20:12:26Z

On 06/08/2010 02:16 PM, Alex Williamson wrote:
> Synchronize RAM blocks with the target and migrate using name/offset
> pairs. This ensures both source and target have the same view of
> RAM and that we get the right bits into the right slot.
>
> Signed-off-by: Alex Williamson<alex.williamson@redhat.com>
> ---
>
> arch_init.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
> vl.c | 2 +
> 2 files changed, 93 insertions(+), 12 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index 6103461..8ba92ec 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -113,20 +113,29 @@ static int ram_save_block(QEMUFile *f)
>
> while (addr< total_ram) {
> if (cpu_physical_memory_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
> + RAMBlock *block;
> + ram_addr_t offset;
> uint8_t *p;
>
> cpu_physical_memory_reset_dirty(current_addr,
> current_addr + TARGET_PAGE_SIZE,
> MIGRATION_DIRTY_FLAG);
>
> - p = qemu_get_ram_ptr(current_addr);
> + QLIST_FOREACH(block,&ram.blocks, next) {
> + if (current_addr - block->offset< block->length)
> + break;
> + }
> + offset = current_addr - block->offset;
> + p = block->host + offset;
>
> if (is_dup_page(p, *p)) {
> - qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
> + qemu_put_be64(f, offset | RAM_SAVE_FLAG_COMPRESS);
> + qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
> qemu_put_byte(f, *p);
>

I think we could use some trickery like use another flag in
current_address to determine whether this was a different section from
the previous section and then only encode the section name if that's true.

Regards,

Anthony Liguori

> bytes_sent = 1;
> } else {
> - qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
> + qemu_put_be64(f, offset | RAM_SAVE_FLAG_PAGE);
> + qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
> qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
> bytes_sent = TARGET_PAGE_SIZE;
> }
> @@ -196,6 +205,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
> }
>
> if (stage == 1) {
> + RAMBlock *block;
> uint64_t total_ram = ram_bytes_total();
> bytes_transferred = 0;
>
> @@ -210,6 +220,11 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
> cpu_physical_memory_set_dirty_tracking(1);
>
> qemu_put_be64(f, total_ram | RAM_SAVE_FLAG_MEM_SIZE);
> +
> + QLIST_FOREACH(block,&ram.blocks, next) {
> + qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
> + qemu_put_be64(f, block->length);
> + }
> }
>
> bytes_transferred_last = bytes_transferred;
> @@ -257,7 +272,7 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
> ram_addr_t addr;
> int flags;
>
> - if (version_id != 3) {
> + if (version_id< 3) {
> return -EINVAL;
> }
>
> @@ -268,23 +283,89 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
> addr&= TARGET_PAGE_MASK;
>
> if (flags& RAM_SAVE_FLAG_MEM_SIZE) {
> - if (addr != ram_bytes_total()) {
> - return -EINVAL;
> + if (version_id == 3) {
> + if (addr != ram_bytes_total()) {
> + return -EINVAL;
> + }
> + } else {
> + /* Synchronize RAM block list */
> + char name[64];
> + ram_addr_t length;
> + ram_addr_t total_ram_bytes = addr;
> +
> + while (total_ram_bytes) {
> + RAMBlock *block;
> + qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> + length = qemu_get_be64(f);
> +
> + QLIST_FOREACH(block,&ram.blocks, next) {
> + if (!strncmp(name, block->name, sizeof(name))) {
> + if (block->length != length)
> + return -EINVAL;
> + break;
> + }
> + }
> +
> + if (!block) {
> + if (!qemu_ram_alloc(name, length))
> + return -ENOMEM;
> + }
> +
> + total_ram_bytes -= length;
> + }
> }
> }
>
> if (flags& RAM_SAVE_FLAG_COMPRESS) {
> - uint8_t ch = qemu_get_byte(f);
> - memset(qemu_get_ram_ptr(addr), ch, TARGET_PAGE_SIZE);
> + void *host;
> + uint8_t ch;
> +
> + if (version_id == 3) {
> + host = qemu_get_ram_ptr(addr);
> + } else {
> + RAMBlock *block;
> + char name[64];
> +
> + qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> +
> + QLIST_FOREACH(block,&ram.blocks, next) {
> + if (!strncmp(name, block->name, sizeof(name)))
> + break;
> + }
> + if (!block)
> + return -EINVAL;
> +
> + host = block->host + addr;
> + }
> + ch = qemu_get_byte(f);
> + memset(host, ch, TARGET_PAGE_SIZE);
> #ifndef _WIN32
> if (ch == 0&&
> (!kvm_enabled() || kvm_has_sync_mmu())) {
> - madvise(qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE,
> - MADV_DONTNEED);
> + madvise(host, TARGET_PAGE_SIZE, MADV_DONTNEED);
> }
> #endif
> } else if (flags& RAM_SAVE_FLAG_PAGE) {
> - qemu_get_buffer(f, qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE);
> + void *host;
> +
> + if (version_id == 3) {
> + host = qemu_get_ram_ptr(addr);
> + } else {
> + RAMBlock *block;
> + char name[64];
> +
> + qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> +
> + QLIST_FOREACH(block,&ram.blocks, next) {
> + if (!strncmp(name, block->name, sizeof(name)))
> + break;
> + }
> + if (!block)
> + return -EINVAL;
> +
> + host = block->host + addr;
> + }
> + qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
> }
> if (qemu_file_has_error(f)) {
> return -EIO;
> diff --git a/vl.c b/vl.c
> index 9e9c176..a871895 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3731,7 +3731,7 @@ int main(int argc, char **argv, char **envp)
> if (qemu_opts_foreach(&qemu_drive_opts, drive_init_func, machine, 1) != 0)
> exit(1);
>
> - register_savevm_live("ram", 0, 3, NULL, ram_save_live, NULL,
> + register_savevm_live("ram", 0, 4, NULL, ram_save_live, NULL,
> ram_load, NULL);
>
> if (nb_numa_nodes> 0) {
>
>