From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
David Rientjes <rientjes@google.com>
Subject: Re: [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map
Date: Thu, 5 Mar 2015 15:21:35 -0800 [thread overview]
Message-ID: <20150305232135.GE30570@linux.vnet.ibm.com> (raw)
In-Reply-To: <20150305220804.GF23912@htj.duckdns.org>
On 05.03.2015 [17:08:04 -0500], Tejun Heo wrote:
> Hello,
>
> On Thu, Mar 05, 2015 at 01:58:27PM -0800, David Rientjes wrote:
> > I'm not sure why this is being proposed as a powerpc patch and now a patch
> > for mem_cgroup_css_alloc(). In other words, why do we have to allocate
> > for all possible nodes? We should only be allocating for online nodes in
> > N_MEMORY with mem hotplug disabled initially and then have a mem hotplug
> > callback implemented to alloc_mem_cgroup_per_zone_info() for nodes that
> > transition from memoryless -> memory. The extra bonus is that
> > alloc_mem_cgroup_per_zone_info() need never allocate remote memory and the
> > TODO in that function can be removed.
>
> For cpus, the general direction is allocating for all possible cpus.
> For iterations, we alternate between using all possibles and onlines
> depending on the use case; however, the general idea is that the
> possibles and onlines aren't gonna be very different. NR_CPUS and
> MAX_NUMNODES gotta accomodate the worst possible case the kernel may
> run on but the possible masks should be set to the actually possible
> subset during boot so that the kernel don't end up allocating for and
> iterating over things which can't ever exist.
Makes sense to me.
> It can be argued that we should always stick to the online masks for
> allocation and iteration; however, that usually requires more
> complexity and the only cases where this mattered have been when the
> boot code got it wrong and failed to set the possible masks correctly,
> which also seems to be the case here. I don't see any reason to
> deviate here.
So, do you agree with the general direction of my change? :)
Thanks,
Nish
next prev parent reply other threads:[~2015-03-05 23:22 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-05 18:05 [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Nishanth Aravamudan
2015-03-05 21:16 ` David Rientjes
2015-03-05 21:48 ` Michael Ellerman
2015-03-05 21:58 ` David Rientjes
2015-03-05 22:08 ` Tejun Heo
2015-03-05 22:18 ` Tejun Heo
2015-03-05 23:21 ` Nishanth Aravamudan [this message]
2015-03-05 23:24 ` Tejun Heo
2015-03-05 23:20 ` Nishanth Aravamudan
2015-03-05 23:17 ` Nishanth Aravamudan
2015-03-05 23:15 ` Nishanth Aravamudan
2015-03-05 23:29 ` David Rientjes
2015-03-06 5:27 ` [PATCH v2] powerpc/numa: set node_possible_map to only node_online_map during boot Nishanth Aravamudan
2015-03-06 11:29 ` Raghavendra K T
2015-03-09 23:55 ` Michael Ellerman
2015-03-10 23:50 ` [PATCH v3] " Nishanth Aravamudan
2015-03-05 22:13 ` [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Tejun Heo
2015-03-05 23:27 ` Nishanth Aravamudan
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