From: Neil Zhang <zhangwm@marvell.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Dan Streetman <ddstreet@ieee.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] drivers: base: update cpu offline info when do hotplug
Date: Sun, 26 Oct 2014 19:17:14 -0700 [thread overview]
Message-ID: <9034CBD80F070943B59700D7F8149ED9024ED2A13D@SC-VEXCH4.marvell.com> (raw)
In-Reply-To: <20141027015836.GA27978@kroah.com>
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> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: 2014年10月27日 9:59
> To: Neil Zhang
> Cc: Dan Streetman; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] drivers: base: update cpu offline info when do hotplug
>
> On Sun, Oct 26, 2014 at 06:43:11PM -0700, Neil Zhang wrote:
> > Greg,
> >
> >
> > > -----Original Message-----
> > > From: ddstreet@gmail.com [mailto:ddstreet@gmail.com] On Behalf Of
> > > Dan Streetman
> > > Sent: 2014年10月21日 1:03
> > > To: Neil Zhang
> > > Cc: Greg KH; linux-kernel@vger.kernel.org
> > > Subject: Re: [PATCH] drivers: base: update cpu offline info when do
> > > hotplug
> > >
> > > On Mon, Oct 20, 2014 at 3:40 AM, Neil Zhang <zhangwm@marvell.com> wrote:
> > > > Greg,
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Greg KH [mailto:gregkh@linuxfoundation.org]
> > > > Sent: 2014年10月20日 14:48
> > > > To: Neil Zhang
> > > > Cc: linux-kernel@vger.kernel.org
> > > > Subject: Re: [PATCH] drivers: base: update cpu offline info when
> > > > do hotplug
> > > >
> > > > On Sun, Oct 19, 2014 at 11:39:23PM -0700, Neil Zhang wrote:
> > > >>> How much noise is this going to cause on a big/little system
> > > >>> that constantly hot unplug/plugs processors all of the time?
> > > >>
> > > >> Can you explain more what kind of noise will be introduced on a
> > > >> big/little
> > > system?
> > > >
> > > > Have you tested this on such a machine?
> > > >
> > > > I didn't have such kind of machine on hand.
> > > > Can anyone has such machine to verify it?
> > > > Thanks!
> > >
> > > I tested this on a ppc PowerVM system, using dlpar operations to
> > > remove/add cpus.
> > >
> > > Without this patch the cpu online nodes get out of sync with the
> > > main online node (and the actual state of the cpus), because they
> > > aren't updated as the cpus are brought up/down:
> > >
> > > [root@br10p02 cpu]$ pwd
> > > /sys/devices/system/cpu
> > > [root@br10p02 cpu]$ cat online
> > > 0-39
> > > [root@br10p02 cpu]$ for n in {0..47} ; do test $( cat cpu$n/online )
> > > -eq 1 && echo -n "$n " ; done ; echo ""
> > > 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
> > > 26
> > > 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
> > >
> > >
> > > While with the patch, the cpu online nodes are kept up to date as
> > > the cpus are brought up/down:
> > >
> > > [root@br10p02 cpu]$ pwd
> > > /sys/devices/system/cpu
> > > [root@br10p02 cpu]$ cat online
> > > 0-39
> > > [root@br10p02 cpu]$ for n in {0..47} ; do test $( cat cpu$n/online )
> > > -eq 1 && echo -n "$n " ; done ; echo ""
> > > 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
> > > 26
> > > 27 28 29 30 31 32 33 34 35 36 37 38 39
> > >
> > >
> > > Feel free to add
> > >
> > > Tested-by: Dan Streetman <ddstreet@ieee.org>
> > >
> >
> > It's a real bug in the kernel.
>
> As this has been this way for many years, I tend to think it's not all that
> important...
Actually this bug was introduced by the following patch.
commit 0902a9044fa5b7a0456ea4daacec2c2b3189ba8c
Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Date: Fri May 3 00:25:49 2013 +0200
Driver core: Use generic offline/online for CPU offline/online
So seems not that long :)
>
> > What's your comments about this patch?
>
> It's one of 1800+ patches that need my comments, please be patient.
Got it, thanks!
>
> greg k-h
Best Regards,
Neil Zhang
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next prev parent reply other threads:[~2014-10-27 2:17 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-20 3:29 [PATCH] drivers: base: update cpu offline info when do hotplug Neil Zhang
2014-10-20 4:43 ` Greg KH
2014-10-20 6:39 ` Neil Zhang
2014-10-20 6:48 ` Greg KH
2014-10-20 7:40 ` Neil Zhang
2014-10-20 17:02 ` Dan Streetman
2014-10-21 0:47 ` Neil Zhang
2014-10-21 2:57 ` Yasuaki Ishimatsu
2014-10-21 3:18 ` Neil Zhang
2014-10-21 3:26 ` Yasuaki Ishimatsu
2014-10-21 3:36 ` Neil Zhang
2014-10-21 4:47 ` Yasuaki Ishimatsu
2014-10-21 12:58 ` Dan Streetman
2014-10-27 1:43 ` Neil Zhang
2014-10-27 1:58 ` Greg KH
2014-10-27 2:17 ` Neil Zhang [this message]
2014-10-27 2:26 ` Greg KH
2014-10-27 2:30 ` Neil Zhang
2014-10-27 16:28 ` Dan Streetman
2014-10-21 13:02 ` Dan Streetman
2014-10-22 1:32 ` Neil Zhang
2014-10-23 14:05 ` Dan Streetman
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