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Date: Fri, 31 Aug 2018 04:53:50 -0700
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
 Mel Gorman <mgorman@techsingularity.net>,
 Rik van Riel <riel@surriel.com>, Thomas Gleixner <tglx@linutronix.de>,
 Michael Ellerman <mpe@ellerman.id.au>,
 Heiko Carstens <heiko.carstens@de.ibm.com>,
 Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
 linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
 Benjamin Herrenschmidt <benh@au1.ibm.com>
Subject: Re: [PATCH 2/2] sched/topology: Expose numa_mask set/clear functions
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* Peter Zijlstra <peterz@infradead.org> [2018-08-31 13:26:39]:

> On Fri, Aug 31, 2018 at 01:12:53PM +0200, Peter Zijlstra wrote:
> > NAK, not until you've fixed every cpu_to_node() user in the kernel to
> > deal with that mask changing.
> 
> Also, what happens if userspace reads that information; uses libnuma and
> then you go and shift the world underneath their feet?
> 
> > This is absolutely insane.
> 

The topology events are suppose to be very rare.
>>From whatever small experiments I have done till now, unless tasks are
bound to both cpu and memory, they seem to be coping well with topology
updates. I know things weren't optimal after a topology change but they
worked. Now after 051f3ca02e46 "Introduce NUMA identity node sched
domain", systems stall. I am only exploring at ways to keep them working
as much as they were before that commit.

-- 
Thanks and Regards
Srikar Dronamraju