From 48df9d8002914137b0a1e5c4ca4d402224f205f9 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Thu, 6 Sep 2018 15:00:59 +0800 Subject: [PATCH] migration: do not flush_compressed_data at the end of iteration flush_compressed_data() needs to wait all compression threads to finish their work, after that all threads are free until the migration feeds new request to them, reducing its call can improve the throughput and use CPU resource more effectively We do not need to flush all threads at the end of iteration, the data can be kept locally until the memory block is changed or memory migration starts over in that case we will meet a dirtied page which may still exists in compression threads's ring Signed-off-by: Xiao Guangrong Reviewed-by: Juan Quintela Message-Id: <20180906070101.27280-2-xiaoguangrong@tencent.com> Signed-off-by: Juan Quintela Signed-off-by: Dr. David Alan Gilbert --- migration/ram.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 43360f6483..2c039892d3 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1996,17 +1996,22 @@ static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool *again) pss->page = 0; pss->block = QLIST_NEXT_RCU(pss->block, next); if (!pss->block) { + /* + * If memory migration starts over, we will meet a dirtied page + * which may still exists in compression threads's ring, so we + * should flush the compressed data to make sure the new page + * is not overwritten by the old one in the destination. + * + * Also If xbzrle is on, stop using the data compression at this + * point. In theory, xbzrle can do better than compression. + */ + flush_compressed_data(rs); + /* Hit the end of the list */ pss->block = QLIST_FIRST_RCU(&ram_list.blocks); /* Flag that we've looped */ pss->complete_round = true; rs->ram_bulk_stage = false; - if (migrate_use_xbzrle()) { - /* If xbzrle is on, stop using the data compression at this - * point. In theory, xbzrle can do better than compression. - */ - flush_compressed_data(rs); - } } /* Didn't find anything this time, but try again on the new block */ *again = true; @@ -3219,7 +3224,6 @@ static int ram_save_iterate(QEMUFile *f, void *opaque) } i++; } - flush_compressed_data(rs); rcu_read_unlock(); /*