From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43027) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ulz8x-0006dh-Bu for qemu-devel@nongnu.org; Mon, 10 Jun 2013 06:16:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ulz8s-0001ip-En for qemu-devel@nongnu.org; Mon, 10 Jun 2013 06:16:07 -0400 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:45222 helo=mx01.kamp.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1Ulz8s-0001id-4N for qemu-devel@nongnu.org; Mon, 10 Jun 2013 06:16:02 -0400 From: Peter Lieven Date: Mon, 10 Jun 2013 12:14:20 +0200 Message-Id: <1370859260-8183-3-git-send-email-pl@kamp.de> In-Reply-To: <1370859260-8183-1-git-send-email-pl@kamp.de> References: <1370859260-8183-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [PATCHv2 2/2] migration: do not overwrite zero pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: quintela@redhat.com, aik@ozlabs.ru, Peter Lieven , owasserm@redhat.com, pbonzini@redhat.com, xiawenc@linux.vnet.ibm.com, david@gibson.dropbear.id.au on incoming migration do not memset pages to zero if they already read as zero. this will allocate a new zero page and consume memory unnecessarily. even if we madvise a MADV_DONTNEED later this will only deallocate the memory asynchronously. Signed-off-by: Peter Lieven --- arch_init.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch_init.c b/arch_init.c index 08fccf6..cf4e1d5 100644 --- a/arch_init.c +++ b/arch_init.c @@ -832,14 +832,16 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id) } ch = qemu_get_byte(f); - memset(host, ch, TARGET_PAGE_SIZE); + if (ch != 0 || !is_zero_page(host)) { + memset(host, ch, TARGET_PAGE_SIZE); #ifndef _WIN32 - if (ch == 0 && - (!kvm_enabled() || kvm_has_sync_mmu()) && - getpagesize() <= TARGET_PAGE_SIZE) { - qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED); - } + if (ch == 0 && + (!kvm_enabled() || kvm_has_sync_mmu()) && + getpagesize() <= TARGET_PAGE_SIZE) { + qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED); + } #endif + } } else if (flags & RAM_SAVE_FLAG_PAGE) { void *host; -- 1.7.9.5