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Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs
From: |
Orit Wasserman |
Subject: |
Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs |
Date: |
Thu, 21 Mar 2013 18:40:24 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
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 <address@hidden>
>>>
>>> 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
- Re: [Qemu-devel] [PATCH v3 5/9] Use writev ops if available, (continued)
- [Qemu-devel] [PATCH v3 6/9] More optimized qemu_put_be64/32/16, Orit Wasserman, 2013/03/21
- [Qemu-devel] [PATCH v3 7/9] Add qemu_put_buffer_no_copy, Orit Wasserman, 2013/03/21
- [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Orit Wasserman, 2013/03/21
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Juan Quintela, 2013/03/21
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Michael S. Tsirkin, 2013/03/21
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Juan Quintela, 2013/03/21
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Michael S. Tsirkin, 2013/03/21
Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, Juan Quintela, 2013/03/21
[Qemu-devel] [PATCH v3 8/9] Use qemu_put_buffer_no_copy for guest memory pages, Orit Wasserman, 2013/03/21