From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59993) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V9GGT-0004oG-Qd for qemu-devel@nongnu.org; Tue, 13 Aug 2013 11:12:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V9GGN-0003oA-UI for qemu-devel@nongnu.org; Tue, 13 Aug 2013 11:12:05 -0400 Sender: fluxion From: Michael Roth Date: Tue, 13 Aug 2013 10:10:38 -0500 Message-Id: <1376406680-16302-15-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1376406680-16302-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1376406680-16302-1-git-send-email-mdroth@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 14/56] migration: do not overwrite zero pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: aliguori@us.ibm.com, qemu-stable@nongnu.org From: Peter Lieven 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 Signed-off-by: Juan Quintela (cherry picked from commit 211ea74022f51164a7729030b28eec90b6c99a08) Signed-off-by: Michael Roth --- arch_init.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch_init.c b/arch_init.c index 6afc57e..b526dd0 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