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

[Gonglei]

On 2014/10/17 16:33, Daniel P. Berrange wrote:

> On Fri, Oct 17, 2014 at 04:27:17PM +0800, address@hidden wrote:
>> From: linhaifeng <address@hidden>
>>
>> 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 <address@hidden>
> 
> 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.

Best Regards,
-Gonglei