Re: [Qemu-devel] [RFC]QEMU disk I/O limits

[Michal Suchanek <hramrach@centrum.cz>]

On 1 June 2011 05:12, Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> wrote:
> On Tue, May 31, 2011 at 03:55:49PM -0400, Vivek Goyal wrote:
>>Date: Tue, 31 May 2011 15:55:49 -0400
>>From: Vivek Goyal <vgoyal@redhat.com>
>>To: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>>Cc: kwolf@redhat.com, aliguori@us.ibm.com, stefanha@linux.vnet.ibm.com,
>>       kvm@vger.kernel.org, guijianfeng@cn.fujitsu.com,
>>       qemu-devel@nongnu.org, wuzhy@cn.ibm.com,
>>       herbert@gondor.hengli.com.au, luowenj@cn.ibm.com, zhanx@cn.ibm.com,
>>       zhaoyang@cn.ibm.com, llim@redhat.com, raharper@us.ibm.com
>>Subject: Re: [Qemu-devel] [RFC]QEMU disk I/O limits
>>User-Agent: Mutt/1.5.21 (2010-09-15)
>>
>>On Mon, May 30, 2011 at 01:09:23PM +0800, Zhi Yong Wu wrote:
>>
>>[..]
>>>     3.) How the users enable and play with it
>>>     QEMU -drive option will be extended so that disk I/O limits can be specified on its command line, such as -drive [iops=xxx,][throughput=xxx] or -drive [iops_rd=xxx,][iops_wr=xxx,][throughput=xxx] etc. When this argument is specified, it means that "disk I/O limits" feature is enabled for this drive disk.
>>
>>How does throughput interface look like? is it bytes per second or something
>>else?
> HI, Vivek,
> It will be a value based on bytes per second.
>
>>
>>Do we have read and write variants for throughput as we have for iops.
> QEMU code has two variants "rd_bytes, wr_bytes", but we maybe need to get their bytes per second.
>
>>
>>if you have bytes interface(as kenrel does), then "bps_rd" and "bps_wr"
>>might be good names too for thoughput interface.
> I agree with you, and can change them as your suggestions.
>

Changing them this way is not going to be an improvement. While
rd_bytes and wr_bytes lack the time interval specification bps_rd and
bps_wr is ambiguous. Is that bits? bytes? Sure, there should be some
distinction by capitalization but that does not apply since qemu
arguments are all lowercase.

Thanks

Michal