Re: [Qemu-block] [Qemu-devel] [PATCH v3 1/3] qemu-options: explain disk I/O throttling options

[Greg Kurz]

On Wed,  1 Mar 2017 11:50:24 +0000
Stefan Hajnoczi <address@hidden> 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 <address@hidden>
> Cc: Alberto Garcia <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---

Reviewed-by: Greg Kurz <address@hidden>

>  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.
> address@hidden address@hidden,address@hidden,address@hidden
> +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.
> address@hidden address@hidden,address@hidden,address@hidden
> +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.
> address@hidden address@hidden,address@hidden,address@hidden
> +Specify request rate limits in requests per second, either for all request
> +types or for reads or writes only.
> address@hidden address@hidden,address@hidden,address@hidden
> +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.
> address@hidden address@hidden
> +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.
> address@hidden address@hidden
> +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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