On Wed, 1 Mar 2017 11:50:24 +0000 Stefan Hajnoczi <stefa...@redhat.com> wrote:
> The disk I/O throttling options have been listed for a long time but
> never explained on the QEMU man page.
>
> Suggested-by: Nini Gu <n...@redhat.com>
> Cc: Alberto Garcia <be...@igalia.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
Reviewed-by: Greg Kurz <gr...@kaod.org>
> qemu-options.hx | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index c85f77d..bbd1bd9 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -607,6 +607,30 @@ file sectors into the image file.
> conversion of plain zero writes by the OS to driver specific optimized
> zero write commands. You may even choose "unmap" if @var{discard} is set
> to "unmap" to allow a zero write to be converted to an UNMAP operation.
> +@item bps=@var{b},bps_rd=@var{r},bps_wr=@var{w}
> +Specify bandwidth throttling limits in bytes per second, either for all
> request
> +types or for reads or writes only. Small values can lead to timeouts or
> hangs
> +inside the guest. A safe minimum for disks is 2 MB/s.
> +@item bps_max=@var{bm},bps_rd_max=@var{rm},bps_wr_max=@var{wm}
> +Specify bursts in bytes per second, either for all request types or for reads
> +or writes only. Bursts allow the guest I/O to spike above the limit
> +temporarily.
> +@item iops=@var{i},iops_rd=@var{r},iops_wr=@var{w}
> +Specify request rate limits in requests per second, either for all request
> +types or for reads or writes only.
> +@item iops_max=@var{bm},iops_rd_max=@var{rm},iops_wr_max=@var{wm}
> +Specify bursts in requests per second, either for all request types or for
> reads
> +or writes only. Bursts allow the guest I/O to spike above the limit
> +temporarily.
> +@item iops_size=@var{is}
> +Let every @var{is} bytes of a request count as a new request for iops
> +throttling purposes. Use this option to prevent guests from circumventing
> iops
> +limits by sending fewer but larger requests.
> +@item group=@var{g}
> +Join a throttling quota group with given name @var{g}. All drives that are
> +members of the same group are accounted for together. Use this option to
> +prevent guests from circumventing throttling limits by using many small disks
> +instead of a single larger disk.
> @end table
>
> By default, the @option{cache=writeback} mode is used. It will report data
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