* Zhang Chen (zhangc...@gmail.com) wrote:
> During the time of VM's running, PVM may dirty some pages, we will transfer
> PVM's dirty pages to SVM and store them into SVM's RAM cache at next
> checkpoint
> time. So, the content of SVM's RAM cache will always be same with PVM's memory
> after checkpoint.
>
> Instead of flushing all content of PVM's RAM cache into SVM's MEMORY,
> we do this in a more efficient way:
> Only flush any page that dirtied by PVM since last checkpoint.
> In this way, we can ensure SVM's memory same with PVM's.
>
> Besides, we must ensure flush RAM cache before load device state.
>
> Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
> Signed-off-by: Li Zhijian <lizhij...@cn.fujitsu.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/ram.c | 39 +++++++++++++++++++++++++++++++++++++++
> migration/trace-events | 2 ++
> 2 files changed, 41 insertions(+)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index e35dfee06e..4235a8f24d 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3031,6 +3031,40 @@ static bool postcopy_is_running(void)
> return ps >= POSTCOPY_INCOMING_LISTENING && ps < POSTCOPY_INCOMING_END;
> }
>
> +/*
> + * Flush content of RAM cache into SVM's memory.
> + * Only flush the pages that be dirtied by PVM or SVM or both.
> + */
> +static void colo_flush_ram_cache(void)
> +{
> + RAMBlock *block = NULL;
> + void *dst_host;
> + void *src_host;
> + unsigned long offset = 0;
> +
> + trace_colo_flush_ram_cache_begin(ram_state->migration_dirty_pages);
> + rcu_read_lock();
> + block = QLIST_FIRST_RCU(&ram_list.blocks);
> +
> + while (block) {
> + offset = migration_bitmap_find_dirty(ram_state, block, offset);
> + migration_bitmap_clear_dirty(ram_state, block, offset);
That looks suspicious to me; shouldn't that be inside the else block
below? If the find_dirty returns a bit after or equal to used_length
(i.e. there's nothing dirty in this block), then you don't want to clear
that bit yet because it really means there's a dirty page at the start
of the next block?
Dave
> + if (offset << TARGET_PAGE_BITS >= block->used_length) {
> + offset = 0;
> + block = QLIST_NEXT_RCU(block, next);
> + } else {
> + dst_host = block->host + (offset << TARGET_PAGE_BITS);
> + src_host = block->colo_cache + (offset << TARGET_PAGE_BITS);
> + memcpy(dst_host, src_host, TARGET_PAGE_SIZE);
> + }
> + }
> +
> + rcu_read_unlock();
> + trace_colo_flush_ram_cache_end();
> + assert(ram_state->migration_dirty_pages == 0);
> +}
> +
> static int ram_load(QEMUFile *f, void *opaque, int version_id)
> {
> int flags = 0, ret = 0, invalid_flags = 0;
> @@ -3043,6 +3077,7 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> bool postcopy_running = postcopy_is_running();
> /* ADVISE is earlier, it shows the source has the postcopy capability on
> */
> bool postcopy_advised = postcopy_is_advised();
> + bool need_flush = false;
>
> seq_iter++;
>
> @@ -3218,6 +3253,10 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> ret |= wait_for_decompress_done();
> rcu_read_unlock();
> trace_ram_load_complete(ret, seq_iter);
> +
> + if (!ret && migration_incoming_in_colo_state() && need_flush) {
> + colo_flush_ram_cache();
> + }
> return ret;
> }
>
> diff --git a/migration/trace-events b/migration/trace-events
> index 9295b4cf40..8e2f9749e0 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -78,6 +78,8 @@ ram_load_postcopy_loop(uint64_t addr, int flags) "@%"
> PRIx64 " %x"
> ram_postcopy_send_discard_bitmap(void) ""
> ram_save_page(const char *rbname, uint64_t offset, void *host) "%s: offset:
> 0x%" PRIx64 " host: %p"
> ram_save_queue_pages(const char *rbname, size_t start, size_t len) "%s:
> start: 0x%zx len: 0x%zx"
> +colo_flush_ram_cache_begin(uint64_t dirty_pages) "dirty_pages %" PRIu64
> +colo_flush_ram_cache_end(void) ""
>
> # migration/migration.c
> await_return_path_close_on_source_close(void) ""
> --
> 2.17.0
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
