From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49930) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um5ds-0000rT-NJ for qemu-devel@nongnu.org; Mon, 10 Jun 2013 13:12:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Um5dr-0005vy-GH for qemu-devel@nongnu.org; Mon, 10 Jun 2013 13:12:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57551) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Um5dr-0005vs-6i for qemu-devel@nongnu.org; Mon, 10 Jun 2013 13:12:27 -0400 Message-ID: <51B6094E.8020607@redhat.com> Date: Mon, 10 Jun 2013 20:13:50 +0300 From: Orit Wasserman MIME-Version: 1.0 References: <1370859260-8183-1-git-send-email-pl@kamp.de> <1370859260-8183-3-git-send-email-pl@kamp.de> In-Reply-To: <1370859260-8183-3-git-send-email-pl@kamp.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv2 2/2] migration: do not overwrite zero pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: quintela@redhat.com, aik@ozlabs.ru, qemu-devel@nongnu.org, pbonzini@redhat.com, xiawenc@linux.vnet.ibm.com, david@gibson.dropbear.id.au On 06/10/2013 01:14 PM, Peter Lieven wrote: > 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; > > Reviewed-by: Orit Wasserman