linux-kernel - Re: [PATCH part2 v2 0/8] Arrange hotpluggable memory as ZONE

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Date:	Mon, 14 Oct 2013 13:35:50 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>,
	Zhang Yanfei <zhangyanfei.yes@...il.com>
CC:	Tejun Heo <tj@...nel.org>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH part2 v2 0/8] Arrange hotpluggable memory as ZONE_MOVABLE

On 10/14/2013 12:34 PM, Yinghai Lu wrote:
> 
> The points for parsing SRAT early instead of Yanfei/Tang v7:
> 1. We just reached one unified path to setup page tables for 32bit,
> 64bit and xen or non xen after several years. We should not have add
> another path for system
> that support hotplug.
> 
> 2. also we should avoid adding "movable_nodes" command line.
> 
> 3. debug mapping 4k, and it is working all the way, why breaking it even for
> memory hotplug path?
> 
> 4. numa_meminfo now is static structure.
> we have no reason that we can not parse SRAT etc to fill that struct.
> 
> 5. for device tree, i assume that we could do same like srat parsing to find out
> numa to fill the numa_meminfo early. or with help of BRK.
> 
> 6. in the long run, We should rework our NUMA booting:
> a. boot system with boot numa nodes early only.
> b. in later init stage or user space, init other nodes
> RAM/CPU/PCI...in parallel.
> that will reduce boot time for 8 sockets/32 sockets dramatically.
> 
> We will need to parse srat table early so could avoid init memory for
> non-boot nodes.
> 

I really like the long-term plan (and, I might want to add, the above
writeup.)

However, I don't understand how we can avoid #2, given that it is
fundamentally a sysadmin-driven tradeoff between performance and
reliability.

	-hpa

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