[Qemu-devel] memory leak in block/xen_disk in qemu-3.x

[Qemu-devel] memory leak in block/xen_disk in qemu-3.x

[Olaf Hering]

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What are the live time rules of ioreq->buf?

In my testing the memory usage of qemu is constantly growing from about
250MB to several GB after a few days.

Some debugging shows that ioreq_runio_qemu_aio() overwrites ioreq->buf,
which contributes to the leak. In addition, ioreq_reset() also just
globbers iorew->buf. While this was observed with a backport of xen_disk
changes to qemu-2.9, the code in xen_disk.c did not change in this
regard. I changed the code to call qemu_vfree(ioreq->buf) in the few
places that globber the pointer, that fixes the leak for me.

Right now neither qemu-3.0 nor 3.1 for me, so I can not test
qemu.git#master if it eventually behaves different than
qemu.git#stable-2.9+backport.

Olaf

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Re: [Qemu-devel] [Xen-devel] memory leak in block/xen_disk in qemu-3.x

[Paul Durrant]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xenproject.org] On Behalf
> Of Olaf Hering
> Sent: 11 December 2018 15:31
> To: xen-devel@lists.xenproject.org; qemu-devel@nongnu.org
> Subject: [Xen-devel] memory leak in block/xen_disk in qemu-3.x
> 
> What are the live time rules of ioreq->buf?
> 
> In my testing the memory usage of qemu is constantly growing from about
> 250MB to several GB after a few days.

Are you perhaps running into the problem addressed by this patch?

https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg00244.html

  Paul

> 
> Some debugging shows that ioreq_runio_qemu_aio() overwrites ioreq->buf,
> which contributes to the leak. In addition, ioreq_reset() also just
> globbers iorew->buf. While this was observed with a backport of xen_disk
> changes to qemu-2.9, the code in xen_disk.c did not change in this
> regard. I changed the code to call qemu_vfree(ioreq->buf) in the few
> places that globber the pointer, that fixes the leak for me.
> 
> Right now neither qemu-3.0 nor 3.1 for me, so I can not test
> qemu.git#master if it eventually behaves different than
> qemu.git#stable-2.9+backport.
> 
> Olaf

Re: [Qemu-devel] [Xen-devel] memory leak in block/xen_disk in qemu-3.x

[Olaf Hering]

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On Tue, Dec 11, Paul Durrant wrote:

> > -----Original Message-----
> > From: Xen-devel [mailto:xen-devel-bounces@lists.xenproject.org] On Behalf
> > Of Olaf Hering
> > Sent: 11 December 2018 15:31
> > To: xen-devel@lists.xenproject.org; qemu-devel@nongnu.org
> > Subject: [Xen-devel] memory leak in block/xen_disk in qemu-3.x
> > 
> > What are the live time rules of ioreq->buf?
> > In my testing the memory usage of qemu is constantly growing from about
> > 250MB to several GB after a few days.
> Are you perhaps running into the problem addressed by this patch?
> https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg00244.html

This looks like a fix, rather than an improvement.
More than a month passed already, why is it not yet in qemu.git#master?

Olaf

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Re: [Qemu-devel] [Xen-devel] memory leak in block/xen_disk in qemu-3.x

[Paul Durrant]

> -----Original Message-----
> From: Olaf Hering [mailto:olaf@aepfle.de]
> Sent: 11 December 2018 16:08
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: xen-devel@lists.xenproject.org; qemu-devel@nongnu.org
> Subject: Re: [Xen-devel] memory leak in block/xen_disk in qemu-3.x
> 
> On Tue, Dec 11, Paul Durrant wrote:
> 
> > > -----Original Message-----
> > > From: Xen-devel [mailto:xen-devel-bounces@lists.xenproject.org] On
> Behalf
> > > Of Olaf Hering
> > > Sent: 11 December 2018 15:31
> > > To: xen-devel@lists.xenproject.org; qemu-devel@nongnu.org
> > > Subject: [Xen-devel] memory leak in block/xen_disk in qemu-3.x
> > >
> > > What are the live time rules of ioreq->buf?
> > > In my testing the memory usage of qemu is constantly growing from
> about
> > > 250MB to several GB after a few days.
> > Are you perhaps running into the problem addressed by this patch?
> > https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg00244.html
> 
> This looks like a fix, rather than an improvement.
> More than a month passed already, why is it not yet in qemu.git#master?
> 

It was nacked on the basis that xen_disk is legacy. I have re-based it on my series re-working xen_disk and, as soon as that is all acked, I will post the re-based patch.

  Paul

> Olaf