linux-kernel - RE: [PATCH 2/5] vmbus: suppress uevents for hv

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Message-ID: <DM5PR21MB0476EEBDE58FC7500A678979A0630@DM5PR21MB0476.namprd21.prod.outlook.com>
Date:   Mon, 18 Sep 2017 00:02:33 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "leann.ogasawara@...onical.com" <leann.ogasawara@...onical.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [PATCH 2/5] vmbus: suppress uevents for hv_sock devices



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Sunday, September 10, 2017 1:10 AM
> To: KY Srinivasan <kys@...rosoft.com>
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> olaf@...fle.de; apw@...onical.com; vkuznets@...hat.com;
> jasowang@...hat.com; leann.ogasawara@...onical.com;
> marcelo.cerri@...onical.com; Stephen Hemminger
> <sthemmin@...rosoft.com>; Dexuan Cui <decui@...rosoft.com>; Haiyang
> Zhang <haiyangz@...rosoft.com>
> Subject: Re: [PATCH 2/5] vmbus: suppress uevents for hv_sock devices
> 
> On Sat, Sep 09, 2017 at 11:08:46PM -0700, kys@...hange.microsoft.com
> wrote:
> > From: Dexuan Cui <decui@...rosoft.com>
> >
> > 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
> it...
> 
> sorry, am not going to take this patch.

Greg,

This is not a real problem that needs fixing. The test automation triggered this condition.
I will drop this patch and send the rest.

Regards,

K. Y
> 
> greg k-h