* zhanghailiang (zhang.zhanghaili...@huawei.com) wrote:
> This patch will reduce the downtime of VM for the initial process,
> Privously, we copied all these memory in preparing stage of COLO
> while we need to stop VM, which is a time-consuming process.
> Here we optimize it by a trick, back-up every page while in migration
> process while COLO is enabled, though it affects the speed of the
> migration, but it obviously reduce the downtime of back-up all SVM'S
> memory in COLO preparing stage.
>
> Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
I'll queue this as well; I'm going to clean up some minor things:
> ---
> migration/colo.c | 3 +++
> migration/ram.c | 68 +++++++++++++++++++++++++++++++++++-------------
> migration/ram.h | 1 +
> 3 files changed, 54 insertions(+), 18 deletions(-)
>
> diff --git a/migration/colo.c b/migration/colo.c
> index 93c5a452fb..44942c4e23 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -26,6 +26,7 @@
> #include "qemu/main-loop.h"
> #include "qemu/rcu.h"
> #include "migration/failover.h"
> +#include "migration/ram.h"
> #ifdef CONFIG_REPLICATION
> #include "replication.h"
> #endif
> @@ -845,6 +846,8 @@ void *colo_process_incoming_thread(void *opaque)
> */
> qemu_file_set_blocking(mis->from_src_file, true);
>
> + colo_incoming_start_dirty_log();
> +
> bioc = qio_channel_buffer_new(COLO_BUFFER_BASE_SIZE);
> fb = qemu_fopen_channel_input(QIO_CHANNEL(bioc));
> object_unref(OBJECT(bioc));
> diff --git a/migration/ram.c b/migration/ram.c
> index ed23ed1c7c..ebf9e6ba51 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2277,6 +2277,7 @@ static void ram_list_init_bitmaps(void)
> * dirty_memory[DIRTY_MEMORY_MIGRATION] don't include the whole
> * guest memory.
> */
> +
That change is nice, but shouldn't really be here.
> block->bmap = bitmap_new(pages);
> bitmap_set(block->bmap, 0, pages);
> block->clear_bmap_shift = shift;
> @@ -2986,7 +2987,6 @@ int colo_init_ram_cache(void)
> }
> return -errno;
> }
> - memcpy(block->colo_cache, block->host, block->used_length);
> }
> }
>
> @@ -3000,19 +3000,36 @@ int colo_init_ram_cache(void)
>
> RAMBLOCK_FOREACH_NOT_IGNORED(block) {
> unsigned long pages = block->max_length >> TARGET_PAGE_BITS;
> -
> block->bmap = bitmap_new(pages);
> - bitmap_set(block->bmap, 0, pages);
> }
> }
> - ram_state = g_new0(RAMState, 1);
> - ram_state->migration_dirty_pages = 0;
> - qemu_mutex_init(&ram_state->bitmap_mutex);
> - memory_global_dirty_log_start();
>
> + ram_state_init(&ram_state);
> return 0;
> }
>
> +/* TODO: duplicated with ram_init_bitmaps */
> +void colo_incoming_start_dirty_log(void)
> +{
> + RAMBlock *block = NULL;
> + /* For memory_global_dirty_log_start below. */
> + qemu_mutex_lock_iothread();
> + qemu_mutex_lock_ramlist();
> +
> + memory_global_dirty_log_sync();
> + WITH_RCU_READ_LOCK_GUARD() {
> + RAMBLOCK_FOREACH_NOT_IGNORED(block) {
> + ramblock_sync_dirty_bitmap(ram_state, block);
> + /* Discard this dirty bitmap record */
> + bitmap_zero(block->bmap, block->max_length >> TARGET_PAGE_BITS);
> + }
> + memory_global_dirty_log_start();
> + }
> + ram_state->migration_dirty_pages = 0;
> + qemu_mutex_unlock_ramlist();
> + qemu_mutex_unlock_iothread();
> +}
> +
> /* It is need to hold the global lock to call this helper */
> void colo_release_ram_cache(void)
> {
> @@ -3032,9 +3049,7 @@ void colo_release_ram_cache(void)
> }
> }
> }
> - qemu_mutex_destroy(&ram_state->bitmap_mutex);
> - g_free(ram_state);
> - ram_state = NULL;
> + ram_state_cleanup(&ram_state);
> }
>
> /**
> @@ -3302,7 +3317,6 @@ static void colo_flush_ram_cache(void)
> ramblock_sync_dirty_bitmap(ram_state, block);
> }
> }
> -
I'll remove that
> trace_colo_flush_ram_cache_begin(ram_state->migration_dirty_pages);
> WITH_RCU_READ_LOCK_GUARD() {
> block = QLIST_FIRST_RCU(&ram_list.blocks);
> @@ -3348,7 +3362,7 @@ static int ram_load_precopy(QEMUFile *f)
>
> while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
> ram_addr_t addr, total_ram_bytes;
> - void *host = NULL;
> + void *host = NULL, *host_bak = NULL;
> uint8_t ch;
>
> /*
> @@ -3379,20 +3393,35 @@ static int ram_load_precopy(QEMUFile *f)
> RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) {
> RAMBlock *block = ram_block_from_stream(f, flags);
>
> + host = host_from_ram_block_offset(block, addr);
> /*
> - * After going into COLO, we should load the Page into
> colo_cache.
> + * After going into COLO stage, we should not load the page
> + * into SVM's memory diretly, we put them into colo_cache
> firstly.
^ typo - c
> + * NOTE: We need to keep a copy of SVM's ram in colo_cache.
> + * Privously, we copied all these memory in preparing stage of
> COLO
^ typo - e
> + * while we need to stop VM, which is a time-consuming process.
> + * Here we optimize it by a trick, back-up every page while in
> + * migration process while COLO is enabled, though it affects the
> + * speed of the migration, but it obviously reduce the downtime
> of
> + * back-up all SVM'S memory in COLO preparing stage.
> */
> - if (migration_incoming_in_colo_state()) {
> - host = colo_cache_from_block_offset(block, addr);
> - } else {
> - host = host_from_ram_block_offset(block, addr);
> + if (migration_incoming_colo_enabled()) {
> + if (migration_incoming_in_colo_state()) {
> + /* In COLO stage, put all pages into cache temporarily */
> + host = colo_cache_from_block_offset(block, addr);
> + } else {
> + /*
> + * In migration stage but before COLO stage,
> + * Put all pages into both cache and SVM's memory.
> + */
> + host_bak = colo_cache_from_block_offset(block, addr);
> + }
> }
> if (!host) {
> error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
> ret = -EINVAL;
> break;
> }
> -
> if (!migration_incoming_in_colo_state()) {
> ramblock_recv_bitmap_set(block, host);
> }
> @@ -3506,6 +3535,9 @@ static int ram_load_precopy(QEMUFile *f)
> if (!ret) {
> ret = qemu_file_get_error(f);
> }
> + if (!ret && host_bak) {
> + memcpy(host_bak, host, TARGET_PAGE_SIZE);
> + }
> }
>
> ret |= wait_for_decompress_done();
> diff --git a/migration/ram.h b/migration/ram.h
> index a553d40751..5ceaff7cb4 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -66,5 +66,6 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock
> *rb);
> /* ram cache */
> int colo_init_ram_cache(void);
> void colo_release_ram_cache(void);
> +void colo_incoming_start_dirty_log(void);
>
> #endif
> --
> 2.21.0
>
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
