From: Peter Zijlstra <peterz@infradead•org>
To: Srikar Dronamraju <srikar@linux•vnet.ibm.com>
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 to arch
Date: Fri, 31 Aug 2018 14:05:22 +0200 [thread overview]
Message-ID: <20180831120522.GL24124@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180831115350.GC8437@linux.vnet.ibm.com>
On Fri, Aug 31, 2018 at 04:53:50AM -0700, Srikar Dronamraju wrote:
> * 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.
I'm saying things were fundamentally buggered and this just made it show.
If you cannot guarantee cpu:node relations, you do not have NUMA, end of
story.
next prev parent reply other threads:[~2018-08-31 12:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <reply-to=<20180808081942.GA37418@linux.vnet.ibm.com>
2018-08-10 17:00 ` [PATCH 1/2] sched/topology: Set correct numa topology type Srikar Dronamraju
2018-08-10 17:00 ` [PATCH 2/2] sched/topology: Expose numa_mask set/clear functions to arch Srikar Dronamraju
2018-08-29 8:02 ` Peter Zijlstra
2018-08-31 10:27 ` Srikar Dronamraju
2018-08-31 11:12 ` Peter Zijlstra
2018-08-31 11:26 ` Peter Zijlstra
2018-08-31 11:53 ` Srikar Dronamraju
2018-08-31 12:05 ` Peter Zijlstra [this message]
2018-08-31 12:08 ` Peter Zijlstra
2018-08-21 11:02 ` [PATCH 1/2] sched/topology: Set correct numa topology type Srikar Dronamraju
2018-08-21 13:59 ` Peter Zijlstra
2018-09-10 10:06 ` [tip:sched/core] sched/topology: Set correct NUMA " tip-bot for Srikar Dronamraju
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