From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43668) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIjPr-0000V0-Qm for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:36:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIjPp-0007v7-4q for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:36:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51434) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIjPo-0007v0-SX for qemu-devel@nongnu.org; Thu, 21 Mar 2013 13:36:37 -0400 Message-ID: <514B37F8.80804@redhat.com> Date: Thu, 21 Mar 2013 18:40:24 +0200 From: Orit Wasserman MIME-Version: 1.0 References: <1363881940-27505-1-git-send-email-owasserm@redhat.com> <1363881940-27505-10-git-send-email-owasserm@redhat.com> <20130321161608.GE1925@redhat.com> <514B34FE.6010901@redhat.com> <20130321162912.GH1925@redhat.com> In-Reply-To: <20130321162912.GH1925@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: pbonzini@redhat.com, chegu_vinod@hp.com, qemu-devel@nongnu.org, quintela@redhat.com On 03/21/2013 06:29 PM, Michael S. Tsirkin wrote: > On Thu, Mar 21, 2013 at 06:27:42PM +0200, Orit Wasserman wrote: >> On 03/21/2013 06:16 PM, Michael S. Tsirkin wrote: >>> On Thu, Mar 21, 2013 at 06:05:40PM +0200, Orit Wasserman wrote: >>>> This way we send one big buffer instead of many small ones >>>> >>>> Signed-off-by: Orit Wasserman >>> >>> Why does this happen BTW? >> >> It happens in the last phase when we send the device state that consists of a lot >> bytes and int field that are written using qemu_put_byte/be16/... >> > > Confused I thought device_state does not use _nocopy? > My idea of using vmsplice relies exactly on this: > we can not splice device state ... qemu_put_buffer calls qemu_put_buffer_no_copy (you know code reuse) So I guess we will need to add some flag if we want to use vmsplice or not or split no_copy into external and internal. It won't be a big change > >>> >>>> --- >>>> savevm.c | 21 +++++++++++++++++---- >>>> 1 file changed, 17 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/savevm.c b/savevm.c >>>> index 50e8fb2..13a533b 100644 >>>> --- a/savevm.c >>>> +++ b/savevm.c >>>> @@ -634,8 +634,14 @@ void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size) >>>> abort(); >>>> } >>>> >>>> - f->iov[f->iovcnt].iov_base = (uint8_t *)buf; >>>> - f->iov[f->iovcnt++].iov_len = size; >>>> + /* check for adjoint buffer and colace them */ >>>> + if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base + >>>> + f->iov[f->iovcnt - 1].iov_len) { >>>> + f->iov[f->iovcnt - 1].iov_len += size; >>>> + } else { >>>> + f->iov[f->iovcnt].iov_base = (uint8_t *)buf; >>>> + f->iov[f->iovcnt++].iov_len = size; >>>> + } >>>> >>>> f->is_write = 1; >>>> f->bytes_xfer += size; >>>> @@ -690,8 +696,15 @@ void qemu_put_byte(QEMUFile *f, int v) >>>> f->buf[f->buf_index++] = v; >>>> f->is_write = 1; >>>> f->bytes_xfer += 1; >>>> - f->iov[f->iovcnt].iov_base = f->buf + (f->buf_index - 1); >>>> - f->iov[f->iovcnt++].iov_len = 1; >>>> + >>>> + /* check for adjoint buffer and colace them */ >>>> + if (f->iovcnt > 0 && f->buf + (f->buf_index - 1) == >>>> + f->iov[f->iovcnt - 1].iov_base + f->iov[f->iovcnt - 1].iov_len) { >>>> + f->iov[f->iovcnt - 1].iov_len += 1; >>>> + } else { >>>> + f->iov[f->iovcnt].iov_base = f->buf + (f->buf_index - 1); >>>> + f->iov[f->iovcnt++].iov_len = 1; >>>> + } >>>> >>>> if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) { >>>> qemu_fflush(f); >>>> -- >>>> 1.7.11.7