during bulk stage of ram migration if a page is a zero page do not send it at all. the memory at the destination reads as zero anyway.
even if there is an madvise with QEMU_MADV_DONTNEED at the target upon receival of a zero page I have observed that the target starts swapping if the memory is overcommitted. it seems that the pages are dropped asynchronously. Signed-off-by: Peter Lieven <[email protected]> --- arch_init.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch_init.c b/arch_init.c index e5531e8..a3dc20d 100644 --- a/arch_init.c +++ b/arch_init.c @@ -432,9 +432,11 @@ static int ram_save_block(QEMUFile *f, bool last_stage) bytes_sent = -1; if (buffer_is_zero(p, TARGET_PAGE_SIZE)) { acct_info.dup_pages++; - bytes_sent = save_block_hdr(f, block, offset, cont, - RAM_SAVE_FLAG_COMPRESS); - qemu_put_byte(f, *p); + if (!ram_bulk_stage) { + bytes_sent = save_block_hdr(f, block, offset, cont, + RAM_SAVE_FLAG_COMPRESS); + qemu_put_byte(f, *p); + } bytes_sent += 1; } else if (migrate_use_xbzrle()) { current_addr = block->offset + offset; -- 1.7.9.5
