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Re: [Qemu-devel] [PATCH v3 0/2] The intro for QEMU disk I/O limits


From: Zhi Yong Wu
Subject: Re: [Qemu-devel] [PATCH v3 0/2] The intro for QEMU disk I/O limits
Date: Mon, 1 Aug 2011 14:37:40 +0800

On Mon, Aug 1, 2011 at 3:09 AM, Ryan Harper <address@hidden> wrote:
> * Zhi Yong Wu <address@hidden> [2011-07-28 05:53]:
>> The main goal of the patch is to effectively cap the disk I/O speed or 
>> counts of one single VM.It is only one draft, so it unavoidably has some 
>> drawbacks, if you catch them, please let me know.
>>
>> The patch will mainly introduce one block I/O throttling algorithm, one 
>> timer and one block queue for each I/O limits enabled drive.
>>
>> When a block request is coming in, the throttling algorithm will check if 
>> its I/O rate or counts exceed the limits; if yes, then it will enqueue to 
>> the block queue; The timer will periodically handle the I/O requests in it.
>>
>> Some available features follow as below:
>> (1) global bps limit.
>>     -drive bps=xxx            in bytes/s
>> (2) only read bps limit
>>     -drive bps_rd=xxx         in bytes/s
>> (3) only write bps limit
>>     -drive bps_wr=xxx         in bytes/s
>> (4) global iops limit
>>     -drive iops=xxx           in ios/s
>> (5) only read iops limit
>>     -drive iops_rd=xxx        in ios/s
>> (6) only write iops limit
>>     -drive iops_wr=xxx        in ios/s
>> (7) the combination of some limits.
>>     -drive bps=xxx,iops=xxx
>>
>> Known Limitations:
>> (1) #1 can not coexist with #2, #3
>> (2) #4 can not coexist with #5, #6
>> (3) When bps/iops limits are specified to a small value such as 511 bytes/s, 
>> this VM will hang up. We are considering how to handle this senario.
>>
>
> I don't yet have detailed info , but we've got a memory leak in the
> code.  After running the VM with a 1MB r and w limit for 8 hours or
> so:
>
> -drive bps_rd=$((1*1024*1024)),bps_wr=$((1*1024*1024))
>
> I've got my system swapping with 43G resident in memory:
>
> 9913 root      20   0 87.3g  43g  548 D  9.6 34.5  44:00.87 qemu-system-x86
>
>
> would be worth looking through the code and maybe a valgrind run to
> catch the leak.
Sorry, it doesn't free the acb structure mallocated in block queue.
For this issue, after the testing is done, the code V4 has sent out. I
will apply your trace testing. thanks.

Regards,

Zhiyong Wu
>
>
> --
> Ryan Harper
> Software Engineer; Linux Technology Center
> IBM Corp., Austin, Tx
> address@hidden
>



-- 
Regards,

Zhi Yong Wu



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