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Message-ID: <5089E9CA.3060809@cn.fujitsu.com>
Date: Fri, 26 Oct 2012 09:39:22 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: KOSAKI Motohiro <kosaki.motohiro@...il.com>
CC: linux-kernel@...r.kernel.org, Rob Landley <rob@...dley.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Jiang Liu <jiang.liu@...wei.com>,
Jianguo Wu <wujianguo@...wei.com>,
Kay Sievers <kay.sievers@...y.org>,
Greg Kroah-Hartman <gregkh@...e.de>,
Xishi Qiu <qiuxishi@...wei.com>, Mel Gorman <mgorman@...e.de>,
linux-doc@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/3] memory_hotplug: fix stale node_states[N_NORMAL_MEMORY]
Hi, KOSAKI
On 09/28/2012 06:03 AM, KOSAKI Motohiro wrote:
> (9/27/12 2:47 AM), Lai Jiangshan wrote:
>> Currently memory_hotplug only manages the node_states[N_HIGH_MEMORY],
>> it forgets to manage node_states[N_NORMAL_MEMORY]. it causes
>> node_states[N_NORMAL_MEMORY] becomes stale.
>
> What's mean 'stale'? I guess
>
> : Currently memory_hotplug doesn't turn on/off node_states[N_NORMAL_MEMORY]
Right.
> and
> : then it will be invalid if the platform has highmem. Luckily, almost memory
> : hotplug aware platform don't have highmem, but are not all.
>
> right?
Some platforms(32 bit) support logic-memory-hotplug.
Some platforms have movable memory.
They are all considered.
> I supporse this patch only meaningful on ARM platform practically.
>
any platform whic supports memory-hotplug.
>
>
>> We add check_nodemasks_changes_online() and check_nodemasks_changes_offline()
>> to detect whether node_states[N_HIGH_MEMORY] and node_states[N_NORMAL_MEMORY]
>> are changed while hotpluging.
>
>
>> Also add @status_change_nid_normal to struct memory_notify, thus
>> the memory hotplug callbacks know whether the node_states[N_NORMAL_MEMORY]
>> are changed.
>
> status_change_nid_normal is very ugly to me. When status_change_nid and
> status_change_nid_normal has positive value, they are always the same.
> nid and flags value are more natual to me.
If we use flags, the semantic of "status_change_nid" is changed and we need to
change more current code, and we will add complicated to the memory hotplug
callbacks.
like this:
- node = arg->status_change_nid;
+ if (arg->status_change_flags & (1UL << N_HIGH_MEMORY))
+ node = arg->status_change_nid;
+ else
+ node = -1;
>
>
>
>>
>> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
>> ---
>> Documentation/memory-hotplug.txt | 5 ++-
>> include/linux/memory.h | 1 +
>> mm/memory_hotplug.c | 94 +++++++++++++++++++++++++++++++------
>> 3 files changed, 83 insertions(+), 17 deletions(-)
>>
>> diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
>> index 6d0c251..6e6cbc7 100644
>> --- a/Documentation/memory-hotplug.txt
>> +++ b/Documentation/memory-hotplug.txt
>> @@ -377,15 +377,18 @@ The third argument is passed by pointer of struct memory_notify.
>> struct memory_notify {
>> unsigned long start_pfn;
>> unsigned long nr_pages;
>> + int status_change_nid_normal;
>> int status_change_nid;
>> }
>>
>> start_pfn is start_pfn of online/offline memory.
>> nr_pages is # of pages of online/offline memory.
>> +status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask
>> +is (will be) set/clear, if this is -1, then nodemask status is not changed.
>> status_change_nid is set node id when N_HIGH_MEMORY of nodemask is (will be)
>> set/clear. It means a new(memoryless) node gets new memory by online and a
>> node loses all memory. If this is -1, then nodemask status is not changed.
>> -If status_changed_nid >= 0, callback should create/discard structures for the
>> +If status_changed_nid* >= 0, callback should create/discard structures for the
>> node if necessary.
>>
>> --------------
>> diff --git a/include/linux/memory.h b/include/linux/memory.h
>> index ff9a9f8..a09216d 100644
>> --- a/include/linux/memory.h
>> +++ b/include/linux/memory.h
>> @@ -53,6 +53,7 @@ int arch_get_memory_phys_device(unsigned long start_pfn);
>> struct memory_notify {
>> unsigned long start_pfn;
>> unsigned long nr_pages;
>> + int status_change_nid_normal;
>> int status_change_nid;
>> };
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 6a5b90d..b62d429b 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -460,6 +460,34 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
>> return 0;
>> }
>>
>> +static void check_nodemasks_changes_online(unsigned long nr_pages,
>> + struct zone *zone, struct memory_notify *arg)
>> +{
>> + int nid = zone_to_nid(zone);
>> + enum zone_type zone_last = ZONE_NORMAL;
>> +
>> + if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
>> + zone_last = ZONE_MOVABLE;
>
> This is very strange (or ugly) code. ZONE_MOVABLE don't depend on high mem.
If we don't have HIGHMEM,
any node of N_NORMAL_MEMORY has 0...ZONE_MOVABLE
if we have HIGHMEM,
any node of N_NORMAL_MEMORY has 0...ZONE_NORMAL
>
>
>> +
>> + if (zone_idx(zone) <= zone_last && !node_state(nid, N_NORMAL_MEMORY))
>> + arg->status_change_nid_normal = nid;
>> + else
>> + arg->status_change_nid_normal = -1;
>
> Wrong. The onlined node may only have high mem zone. IOW, think fake numa case etc.
"zone_idx(zone) <= zone_last" checks this case. the result is "else" branch.
>
>
>> +
>> + if (!node_state(nid, N_HIGH_MEMORY))
>> + arg->status_change_nid = nid;
>> + else
>> + arg->status_change_nid = -1;
>> +}
>> +
>> +static void set_nodemasks(int node, struct memory_notify *arg)
>
> Too ugly. just remove this and use node_set_state() directly.
>
>> +{
>> + if (arg->status_change_nid_normal >= 0)
>> + node_set_state(node, N_NORMAL_MEMORY);
>> +
>> + node_set_state(node, N_HIGH_MEMORY);
>> +}
>> +
>>
>> int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>> {
>> @@ -471,13 +499,18 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>> struct memory_notify arg;
>>
>> lock_memory_hotplug();
>> + /*
>> + * This doesn't need a lock to do pfn_to_page().
>> + * The section can't be removed here because of the
>> + * memory_block->state_mutex.
>> + */
>
> Please explain the intention of this comment. We think lock_memory_hotplug() close
> a race against memory offline directly.
I move old code up. the context does not changed.
>
>
>> + zone = page_zone(pfn_to_page(pfn));
>> +
>> arg.start_pfn = pfn;
>> arg.nr_pages = nr_pages;
>> - arg.status_change_nid = -1;
>> + check_nodemasks_changes_online(nr_pages, zone, &arg);
>>
>> nid = page_to_nid(pfn_to_page(pfn));
>> - if (node_present_pages(nid) == 0)
>> - arg.status_change_nid = nid;
>>
>> ret = memory_notify(MEM_GOING_ONLINE, &arg);
>> ret = notifier_to_errno(ret);
>> @@ -487,12 +520,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>> return ret;
>> }
>> /*
>> - * This doesn't need a lock to do pfn_to_page().
>> - * The section can't be removed here because of the
>> - * memory_block->state_mutex.
>> - */
>> - zone = page_zone(pfn_to_page(pfn));
>> - /*
>> * If this zone is not populated, then it is not in zonelist.
>> * This means the page allocator ignores this zone.
>> * So, zonelist must be updated after online.
>> @@ -517,7 +544,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>> zone->present_pages += onlined_pages;
>> zone->zone_pgdat->node_present_pages += onlined_pages;
>> if (onlined_pages) {
>> - node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
>> + set_nodemasks(zone_to_nid(zone), &arg);
>> if (need_zonelists_rebuild)
>> build_all_zonelists(NULL, zone);
>> else
>> @@ -870,6 +897,44 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
>> return offlined;
>> }
>>
>> +static void check_nodemasks_changes_offline(unsigned long nr_pages,
>> + struct zone *zone, struct memory_notify *arg)
>> +{
>
> This should remove ugly memory_notify argument and should be fold
> check_nodemasks_changes_online().
>
>
>> + struct pglist_data *pgdat = zone->zone_pgdat;
>> + unsigned long present_pages = 0;
>> + enum zone_type zt, zone_last = ZONE_NORMAL;
>> +
>> + if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
>> + zone_last = ZONE_MOVABLE;
>> +
>> + for (zt = 0; zt <= zone_last; zt++)
>> + present_pages += pgdat->node_zones[zt].present_pages;
>> + if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
>> + arg->status_change_nid_normal = zone_to_nid(zone);
>> + else
>> + arg->status_change_nid_normal = -1;
>
> Wrong. Think, a zone has both normal and highmem zone and when admin
> only remove highmem area. you should check pfn too.
I checked the pfn via "zone_idx(zone) <= zone_last".
"""zone = page_zone(pfn_to_page(pfn))"""
>
>
>> +
>> + zone_last = ZONE_MOVABLE;
>> + for (; zt <= zone_last; zt++)
>> + present_pages += pgdat->node_zones[zt].present_pages;
>> + if (nr_pages >= present_pages)
>> + arg->status_change_nid = zone_to_nid(zone);
>> + else
>> + arg->status_change_nid = -1;
>> +}
>> +
>> +static void clear_nodemasks(int node, struct memory_notify *arg)
>> +{
>> + if (arg->status_change_nid_normal >= 0)
>> + node_clear_state(node, N_NORMAL_MEMORY);
>> +
>> + if (N_HIGH_MEMORY == N_NORMAL_MEMORY)
>> + return;
>
> You should use #ifdef. otherwise we face unreachable statement warning.
fixed.
>
>> +
>> + if (arg->status_change_nid >= 0)
>> + node_clear_state(node, N_HIGH_MEMORY);
>> +}
>> +
>> static int __ref offline_pages(unsigned long start_pfn,
>> unsigned long end_pfn, unsigned long timeout)
>> {
>> @@ -903,9 +968,7 @@ static int __ref offline_pages(unsigned long start_pfn,
>>
>> arg.start_pfn = start_pfn;
>> arg.nr_pages = nr_pages;
>> - arg.status_change_nid = -1;
>> - if (nr_pages >= node_present_pages(node))
>> - arg.status_change_nid = node;
>> + check_nodemasks_changes_offline(nr_pages, zone, &arg);
>>
>> ret = memory_notify(MEM_GOING_OFFLINE, &arg);
>> ret = notifier_to_errno(ret);
>> @@ -973,10 +1036,9 @@ repeat:
>> if (!populated_zone(zone))
>> zone_pcp_reset(zone);
>>
>> - if (!node_present_pages(node)) {
>> - node_clear_state(node, N_HIGH_MEMORY);
>> + clear_nodemasks(node, &arg);
>> + if (arg.status_change_nid >= 0)
>> kswapd_stop(node);
>> - }
>>
>> vm_total_pages = nr_free_pagecache_pages();
>> writeback_set_ratelimit();
>>
Thank you very much for the review.
And sorry for so late respond.
Thank,
Lai
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