RE: [PATCH 2/5] vmbus: suppress uevents for hv_sock devices
From: KY Srinivasan
Date: Sun Sep 17 2017 - 20:02:45 EST
> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Sunday, September 10, 2017 1:10 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx;
> olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx;
> jasowang@xxxxxxxxxx; leann.ogasawara@xxxxxxxxxxxxx;
> marcelo.cerri@xxxxxxxxxxxxx; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; Dexuan Cui <decui@xxxxxxxxxxxxx>; Haiyang
> Zhang <haiyangz@xxxxxxxxxxxxx>
> Subject: Re: [PATCH 2/5] vmbus: suppress uevents for hv_sock devices
> On Sat, Sep 09, 2017 at 11:08:46PM -0700, kys@xxxxxxxxxxxxxxxxxxxxxx
> > From: Dexuan Cui <decui@xxxxxxxxxxxxx>
> > hv_sock driver is automatically loaded when an application creates an
> > AF_VSOCK socket, so we don't really need to trigger uevents to the user
> > space udevd.
> > And hv_sock devices can appear and disappear frequency, e.g. 100 per
> > second, so triggering the udevents can cause a high cpu utilization of
> > udevd, e.g. 30% on a 2-cpu virtual machine. So let's suppress the
> > uevents to avoid this.
> 100 per second for a struct device? That's crazy, and the uevent is the
> least of your worries. Please fix that, as it's not the correct way to
> use the driver model at all.
> And really, why is uevent taking all that much cpu time anyway? It
> _should_ be pretty fast, unless your distro is doing crazy things with
> sorry, am not going to take this patch.
This is not a real problem that needs fixing. The test automation triggered this condition.
I will drop this patch and send the rest.
> greg k-h