Re: [Qemu-devel] [RFC 10/12] Add qemu_put_buffer_no_copy

[Orit Wasserman <owasserm@redhat.com>]

On 03/23/2013 06:27 PM, Michael R. Hines wrote:
> Can you add a "flag" or something to indicate that the iov pointer belongs to RAM and not to device state?
> 
> That way, I could re-use this code for RDMA - if I see this flag, I will know to send to RDMA.....
This function is called only for ram pages so no need for flag.

Orit
> 
> - Michael
> 
> 
> On 03/21/2013 05:09 AM, Orit Wasserman wrote:
>> This allow us to add a buffer to the iovec to send without copying it
>> into the static buffer.
>>
>> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
>> ---
>>   include/migration/qemu-file.h |  5 +++++
>>   savevm.c                      | 42 ++++++++++++++++++++++++------------------
>>   2 files changed, 29 insertions(+), 18 deletions(-)
>>
>> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
>> index 8d3da9b..5168be2 100644
>> --- a/include/migration/qemu-file.h
>> +++ b/include/migration/qemu-file.h
>> @@ -75,6 +75,11 @@ int qemu_fclose(QEMUFile *f);
>>   int64_t qemu_ftell(QEMUFile *f);
>>   void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
>>   void qemu_put_byte(QEMUFile *f, int v);
>> +/*
>> + * put_buffer without copying the buffer.
>> + * The buffer should be available till it is sent.
>> + */
>> +void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size);
>>
>>   static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
>>   {
>> diff --git a/savevm.c b/savevm.c
>> index 40d96f4..32a506e 100644
>> --- a/savevm.c
>> +++ b/savevm.c
>> @@ -629,6 +629,22 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
>>   {
>>       int l;
>>
>> +    while (size > 0) {
>> +        l = IO_BUF_SIZE - f->buf_index;
>> +        if (l > size) {
>> +            l = size;
>> +        }
>> +        memcpy(f->buf + f->buf_index, buf, l);
>> +        f->buf_index += l;
>> +        f->is_write = 1;
>> +        qemu_put_buffer_no_copy(f, f->buf + (f->buf_index - l), l);
>> +        buf += l;
>> +        size -= l;
>> +    }
>> +}
>> +
>> +void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size)
>> +{
>>       if (f->last_error) {
>>           return;
>>       }
>> @@ -639,24 +655,14 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
>>           abort();
>>       }
>>
>> -    while (size > 0) {
>> -        l = IO_BUF_SIZE - f->buf_index;
>> -        if (l > size)
>> -            l = size;
>> -        memcpy(f->buf + f->buf_index, buf, l);
>> -        f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
>> -        f->iov[f->iovcnt++].iov_len = l;
>> -        f->is_write = 1;
>> -        f->buf_index += l;
>> -        f->bytes_xfer += l;
>> -        buf += l;
>> -        size -= l;
>> -        if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
>> -            qemu_fflush(f);
>> -            if (qemu_file_get_error(f)) {
>> -                break;
>> -            }
>> -        }
>> +    f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
>> +    f->iov[f->iovcnt++].iov_len = size;
>> +
>> +    f->is_write = 1;
>> +    f->bytes_xfer += size;
>> +
>> +    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
>> +        qemu_fflush(f);
>>       }
>>   }
>>
>