Re: [Qemu-devel] [PATCH] fix the memory leak for share hugepage

[Linhaifeng <haifeng.lin@huawei.com>]

On 2014/10/17 16:56, Gonglei wrote:
> On 2014/10/17 16:33, Daniel P. Berrange wrote:
> 
>> On Fri, Oct 17, 2014 at 04:27:17PM +0800, haifeng.lin@huawei.com wrote:
>>> From: linhaifeng <haifeng.lin@huawei.com>
>>>
>>> The VM start with share hugepage should close the hugefile fd
>>> when exit.Because the hugepage fd may be send to other process
>>> e.g vhost-user If qemu not close the fd the other process can
>>> not free the hugepage otherwise exit process,this is ugly,so
>>> qemu should close all shared fd when exit.
>>>
>>> Signed-off-by: linhaifeng <haifeng.lin@huawei.com>
>>
>> Err, all file descriptors are closed automatically when a process
>> exits. So manually calling close(fd) before exit can't have any
>> functional effect on a resource leak.
>>
>> If QEMU has sent the FD to another process, that process has a
>> completely separate copy of the FD. Closing the FD in QEMU will
>> not close the FD in the other process. You need the other process
>> to exit for the copy to be closed.
>>
> 
> Actually, when vhost-user close the FD manually, the hugepage leak too
> unless the vhost-user process exit. So, maybe the FD is not a separate
> copy IMHO, but simply add the ref-count of FD. When QEMU exit,
> because the ref is not zero, the operate system will not free the FD
> automatically, and when vhost-user close the FD, because of the same
> reason, OS will not free FD resource.
> 
> BTW, I don't think this patch is good. When Qemu exit exceptionally,
> sush as 'by kill -9', this problem of memory leak still exist.
> 

So,we should close qemu by 'kill -15' or close with virsh.

> Best Regards,
> -Gonglei
> 
> 
> 
> 
> .
> 



-- 
Regards,
Haifeng