On Mon, Sep 05, 2022 at 08:06:24PM +0800, Ming Lei wrote:
> On Fri, Sep 02, 2022 at 09:06:27AM +0100, Richard W.M. Jones wrote:
> > On Thu, Sep 01, 2022 at 12:14:40PM +0100, Richard W.M. Jones wrote:
> > > On Thu, Sep 01, 2022 at 04:01:39PM +0800, Ming Lei wrote:
> > > > Maybe you should use one nbd disk, which has the closest code path
> > > > with nbdublk.
> > >
> > > Good idea - I have started a heavy test using nbd.ko as the
> > > backing. Let's see what happens after 12 hours or more.
> >
> > This has been running overnight (using nbd.ko) and there are no
> > problems.
> >
> > Since I have seen 2 failures with ublk, I think there is a problem
> > with the kernel driver, although it happens very rarely.
> >
> > My tests were done using 6.0.0-rc3 (dcf8e5633e).
>
> I believe it is still too early to say it is one ublk driver's issue.
>
> The log shows that the following BUG_ON() is triggered, and ublk driver
> is far away with this issue, and zero zspace->isolated is more like
> one zsmalloc issue, and I highly suggest to report to zsmalloc/zram
> community.
>
> static void dec_zspage_isolation(struct zspage *zspage)
> {
> VM_BUG_ON(zspage->isolated == 0);
> zspage->isolated--;
> }
>
> The effect from ublk could be that swap is more frequently or easy to
> trigger since the ublk io code path needs to pin page from ublksrv's
> vm space, and nbd socket could consume more memory too.
>
> BTW, I did run same kernel build workload on ublk-loop for ~20 hours,
> and it did survive without any issue triggered. And all ublk userspace
> block devices share totally same ublk driver io code path.
>
> Also maybe you can try to run the same workload by replacing zram
> swap disk with other swap disk, such as virito-scsi/..., then see if
> it can survive.
I also ran a much longer test over the weekend ... and this time there
was no error. So I don't know what was going on.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
nbdkit - Flexible, fast NBD server with plugins
https://gitlab.com/nbdkit/nbdkit
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