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Re: [Qemu-devel] [PATCH v3 0/9] Migration: Remove copying of guest ram p
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH v3 0/9] Migration: Remove copying of guest ram pages |
Date: |
Thu, 21 Mar 2013 18:42:45 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux) |
Orit Wasserman <address@hidden> wrote:
> 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.
>
> git repository: git://github.com/oritwas/qemu.git sendv_v2
it is still sendv_v2 or sendv_v3 O:-)
> Change from v2:
> Always send data for the iovec even if writev_buffer is not implemented.
> Coalesce adjacent iovecs to create one big buffer from small adjacent buffer.
>
> Changes from v1:
> Use iov_send for socket.
> Make writev_buffer optional and if it is not implemented use put_buffer
>
> Future work: Make number of iovec changeable
>
> Orit Wasserman (9):
> Add QemuFileWritevBuffer QemuFileOps
> Add socket_writev_buffer function
> Update bytes_xfer in qemu_put_byte
> Store the data to send also in iovec
> Use writev ops if available
> More optimized qemu_put_be64/32/16
> Add qemu_put_buffer_no_copy
> Use qemu_put_buffer_no_copy for guest memory pages
> coalesce adjacent iovecs
>
> arch_init.c | 2 +-
> include/migration/qemu-file.h | 12 ++++
> savevm.c | 127
> ++++++++++++++++++++++++++++++++++--------
> 3 files changed, 116 insertions(+), 25 deletions(-)
Really nice series. Just a couple of small nits.
Later, Juan.
- Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs, (continued)
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
Re: [Qemu-devel] [PATCH v3 0/9] Migration: Remove copying of guest ram pages, Paolo Bonzini, 2013/03/21
Re: [Qemu-devel] [PATCH v3 0/9] Migration: Remove copying of guest ram pages,
Juan Quintela <=