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Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram page
From: |
Orit Wasserman |
Subject: |
Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram pages |
Date: |
Thu, 21 Mar 2013 12:05:44 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
On 03/21/2013 11:29 AM, Paolo Bonzini wrote:
> Il 21/03/2013 10:09, Orit Wasserman ha scritto:
>> In migration all data is copied to a static buffer in QEMUFile,
>> this hurts our network bandwidth and CPU usage especially with large guests.
>> We switched to iovec for storing different buffers to send (even a byte
>> field is
>> considered as a buffer) and use writev to send the iovec.
>> writev was chosen (as apposed to sendmsg) because it supprts non socket fds.
>>
>> Guest memory pages are not copied by calling a new function
>> qemu_put_buffer_no_copy.
>> The page header data and device state data are still copied into the static
>> buffer. This data consists of a lot of bytes and integer fields and the
>> static
>> buffer is used to store it during batching.
>> Another improvement is changing qemu_putbe64/32/16 to create a single
>> buffer instead of several byte sized buffer.
>
> Very nice! I just disagree on making writev_buffer mandatory; instead,
> a QemuFileOps could choose between implementing either put_buffer or
> writev_buffer.
This removes the duplicate code you have between
> iov_writev and block_writev_buffer.
Sure, I can change the code that if put_buffer exists to revert to the previous
implementation.
Orit
>
> Thanks,
>
> Paolo
>
>> Orit Wasserman (12):
>> Add iov_writev to use writev to send iovec (also for files)
>> Add QemuFileWritevBuffer QemuFileOps
>> Add socket_writev_buffer function
>> Add stdio_writev_buffer function
>> Add block_writev_buffer function
>> Update bytes_xfer in qemu_put_byte
>> Store the data to send also in iovec
>> Use writev ops instead of put_buffer ops
>> More optimized qemu_put_be64/32/16
>> Add qemu_put_buffer_no_copy
>> Use qemu_put_buffer_no_copy for guest memory pages
>> Bye Bye put_buffer
>>
>> arch_init.c | 2 +-
>> include/migration/qemu-file.h | 20 ++++---
>> include/qemu/iov.h | 12 ++++
>> savevm.c | 130
>> +++++++++++++++++++++++++-----------------
>> util/iov.c | 36 ++++++++++++
>> 5 files changed, 139 insertions(+), 61 deletions(-)
>>
>
- Re: [Qemu-devel] [RFC 07/12] Store the data to send also in iovec, (continued)
[Qemu-devel] [RFC 08/12] Use writev ops instead of put_buffer ops, Orit Wasserman, 2013/03/21
[Qemu-devel] [RFC 09/12] More optimized qemu_put_be64/32/16, Orit Wasserman, 2013/03/21
[Qemu-devel] [RFC 10/12] Add qemu_put_buffer_no_copy, Orit Wasserman, 2013/03/21
[Qemu-devel] [RFC 11/12] Use qemu_put_buffer_no_copy for guest memory pages, Orit Wasserman, 2013/03/21
[Qemu-devel] [RFC 12/12] Bye Bye put_buffer, Orit Wasserman, 2013/03/21
Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram pages, Paolo Bonzini, 2013/03/21
- Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram pages,
Orit Wasserman <=
Re: [Qemu-devel] [RFC 00/12] Migration: Remove copying of guest ram pages, Michael S. Tsirkin, 2013/03/21