linux-kernel - Re: [Lhms-devel] [PATCH 1/10] hot-add-mem x86

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Date:	Tue, 8 Aug 2006 09:31:10 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	kmannth@...ibm.com
Cc:	akpm@...l.org, discuss@...-64.org,
	lhms-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	ak@...e.de
Subject: Re: [Lhms-devel] [PATCH 1/10] hot-add-mem x86_64: acpi motherboard
 fix

On Mon, 07 Aug 2006 11:39:27 -0700
keith mannthey <kmannth@...ibm.com> wrote:

> On Sat, 2006-08-05 at 14:51 +0900, KAMEZAWA Hiroyuki wrote:
> > On Fri, 4 Aug 2006 07:13:51 -0600
> > Keith Mannthey <kmannth@...ibm.com> wrote:
> > > I have worked to integrate the feedback I recived on the last round of patches
> > > and welcome more ideas/advice. Thanks to everyone who has provied input on
> > > these patches already. 
> > > 
> > Just from review...
> > 
> > If new zone , which was empty at boot, are added into the system.
> > build_all_zonelists() has to be called. (see online_pages() in memory_hotplug.c)
> > it looks x86_64's __add_pages() doesn't calles it.
> 
> With RESERVE there are not empty zones.  All zones (including add-areas)
> are setup during boot and hot add areas reserved in the bootmem
> allocator. 
> 
> Zones don't change size there is no adding to the zone just on-lining on
> pages at are already present in the zone. 
>   
Hmm, curious.
please explain. 
==
int __add_pages(struct zone *z, unsigned long start_pfn, unsigned long nr_pages)
{
        int err = -EIO;
        unsigned long pfn;
        unsigned long total = 0, mem = 0;
        for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) {
                if (pfn_valid(pfn)) {
                        online_page(pfn_to_page(pfn));
                        err = 0;
                        mem++;
                }
                total++;
        }
        if (!err) {
                z->spanned_pages += total;
                z->present_pages += mem; -------------------------------(*)
                z->zone_pgdat->node_spanned_pages += total;
                z->zone_pgdat->node_present_pages += mem;
        }
        return err;
}
==
It looks contents of zone is increased at (*). Do I see old code ?

==
static inline int populated_zone(struct zone *zone)
{
        return (!!zone->present_pages);
}
==
"empty zone" I said means a zone which is not populated.

this populated_zone() is used at build_zone_list().
if populated_zone(z)==0, zone "z" is not included into zonelist and zone will be never
used.

-Kame

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