From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41991) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UpFM0-0007o6-Qm for qemu-devel@nongnu.org; Wed, 19 Jun 2013 06:11:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UpFLz-0006EX-SZ for qemu-devel@nongnu.org; Wed, 19 Jun 2013 06:11:04 -0400 Received: from mail-qa0-x22a.google.com ([2607:f8b0:400d:c00::22a]:35448) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UpFLz-0006ER-Fy for qemu-devel@nongnu.org; Wed, 19 Jun 2013 06:11:03 -0400 Received: by mail-qa0-f42.google.com with SMTP id hu16so300358qab.8 for ; Wed, 19 Jun 2013 03:11:03 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <51C183B0.7010909@redhat.com> Date: Wed, 19 Jun 2013 12:10:56 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1370507765-2806-1-git-send-email-pl@kamp.de> <1370507765-2806-3-git-send-email-pl@kamp.de> In-Reply-To: <1370507765-2806-3-git-send-email-pl@kamp.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/2] migration: do not overwrite zero pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: aik@ozlabs.ru, qemu-devel@nongnu.org, quintela@redhat.com Il 06/06/2013 10:36, Peter Lieven ha scritto: > 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; > > Reviewed-by: Paolo Bonzini