Messages in this thread | | | Date | Mon, 27 Oct 2014 09:58:36 +0800 | From | Greg KH <> | Subject | Re: [PATCH] drivers: base: update cpu offline info when do hotplug |
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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...
> What's your comments about this patch?
It's one of 1800+ patches that need my comments, please be patient.
greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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