From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49785) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UkW78-00075S-Ps for qemu-devel@nongnu.org; Thu, 06 Jun 2013 05:04:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UkW70-0006L7-Rw for qemu-devel@nongnu.org; Thu, 06 Jun 2013 05:04:10 -0400 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:38215 helo=mx01.kamp.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1UkW70-0006L0-Jn for qemu-devel@nongnu.org; Thu, 06 Jun 2013 05:04:02 -0400 From: Peter Lieven Date: Thu, 6 Jun 2013 10:36:05 +0200 Message-Id: <1370507765-2806-3-git-send-email-pl@kamp.de> In-Reply-To: <1370507765-2806-1-git-send-email-pl@kamp.de> References: <1370507765-2806-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [PATCH 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: aik@ozlabs.ru, pbonzini@redhat.com, Peter Lieven , quintela@redhat.com 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 283081d..642f241 100644 --- a/arch_init.c +++ b/arch_init.c @@ -821,14 +821,16 @@ 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