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Message-ID: <20170524125500.GG14733@dhcp22.suse.cz>
Date: Wed, 24 May 2017 14:55:00 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>,
Andrea Arcangeli <aarcange@...hat.com>,
Jerome Glisse <jglisse@...hat.com>,
Reza Arbab <arbab@...ux.vnet.ibm.com>,
Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
Andi Kleen <ak@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Daniel Kiper <daniel.kiper@...cle.com>,
Igor Mammedov <imammedo@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/2] mm, memory_hotplug: drop artificial restriction
on online/offline
On Wed 24-05-17 14:44:34, Vlastimil Babka wrote:
> On 05/24/2017 02:24 PM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@...e.com>
> >
> > 74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
> > memory") has added can_offline_normal which checks the amount of
> > memory in !movable zones as long as CONFIG_MOVABLE_NODE is disable.
> > It disallows to offline memory if there is nothing left with a
> > justification that "memory-management acts bad when we have nodes which
> > is online but don't have any normal memory".
> >
> > 74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
> > memory")
>
> That's the same commit as above... one of them should be different?
This used to be two different patches which I decided to fold together
and I didn't realize that both online and offline paths were introduced
by the same patch.
[...]
> Some editing issue?
yes result of merging two commits.
> Otherwise makes sense to me.
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
Thanks! Updated version follows
---
>From 5196f9e206d780ac473075aa0ad88308409f5acb Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Tue, 23 May 2017 10:32:04 +0200
Subject: [PATCH] mm, memory_hotplug: drop artificial restriction on
online/offline
74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL
memory") has introduced a restriction that every numa node has to have
at least some memory in !movable zones before a first movable memory can
be onlined if !CONFIG_MOVABLE_NODE. Likewise_offline_normal checks the
amount of normal memory in !movable zones and it disallows to offline
memory if there is no normal memory left with a justification that
"memory-management acts bad when we have nodes which is online but don't
have any normal memory".
While it is true that not having _any_ memory for kernel allocations on
a NUMA node is far from great and such a node would be quite subotimal
because all kernel allocations will have to fallback to another NUMA
node but there is no reason to disallow such a configuration in
principle.
Besides that there is not really a big difference to have one memblock
for ZONE_NORMAL available or none. With 128MB size memblocks the system
might trash on the kernel allocations requests anyway. It is really
hard to draw a line on how much normal memory is really sufficient so
we have to rely on administrator to configure system sanely therefore
drop the artificial restriction and remove can_offline_normal and
can_online_high_movable altogether.
Acked-by: Acked-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
mm/memory_hotplug.c | 58 -----------------------------------------------------
1 file changed, 58 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 599c675ad538..10052c2fd400 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -763,23 +763,6 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
return 0;
}
-#ifdef CONFIG_MOVABLE_NODE
-/*
- * When CONFIG_MOVABLE_NODE, we permit onlining of a node which doesn't have
- * normal memory.
- */
-static bool can_online_high_movable(int nid)
-{
- return true;
-}
-#else /* CONFIG_MOVABLE_NODE */
-/* ensure every online node has NORMAL memory */
-static bool can_online_high_movable(int nid)
-{
- return node_state(nid, N_NORMAL_MEMORY);
-}
-#endif /* CONFIG_MOVABLE_NODE */
-
/* check which state of node_states will be changed when online memory */
static void node_states_check_changes_online(unsigned long nr_pages,
struct zone *zone, struct memory_notify *arg)
@@ -979,9 +962,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
if (!allow_online_pfn_range(nid, pfn, nr_pages, online_type))
return -EINVAL;
- if (online_type == MMOP_ONLINE_MOVABLE && !can_online_high_movable(nid))
- return -EINVAL;
-
/* associate pfn range with the zone */
zone = move_pfn_range(online_type, nid, pfn, nr_pages);
@@ -1579,41 +1559,6 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
return offlined;
}
-#ifdef CONFIG_MOVABLE_NODE
-/*
- * When CONFIG_MOVABLE_NODE, we permit offlining of a node which doesn't have
- * normal memory.
- */
-static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
-{
- return true;
-}
-#else /* CONFIG_MOVABLE_NODE */
-/* ensure the node has NORMAL memory if it is still online */
-static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
-{
- struct pglist_data *pgdat = zone->zone_pgdat;
- unsigned long present_pages = 0;
- enum zone_type zt;
-
- for (zt = 0; zt <= ZONE_NORMAL; zt++)
- present_pages += pgdat->node_zones[zt].present_pages;
-
- if (present_pages > nr_pages)
- return true;
-
- present_pages = 0;
- for (; zt <= ZONE_MOVABLE; zt++)
- present_pages += pgdat->node_zones[zt].present_pages;
-
- /*
- * we can't offline the last normal memory until all
- * higher memory is offlined.
- */
- return present_pages == 0;
-}
-#endif /* CONFIG_MOVABLE_NODE */
-
static int __init cmdline_parse_movable_node(char *p)
{
#ifdef CONFIG_MOVABLE_NODE
@@ -1741,9 +1686,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
node = zone_to_nid(zone);
nr_pages = end_pfn - start_pfn;
- if (zone_idx(zone) <= ZONE_NORMAL && !can_offline_normal(zone, nr_pages))
- return -EINVAL;
-
/* set above range as isolated */
ret = start_isolate_page_range(start_pfn, end_pfn,
MIGRATE_MOVABLE, true);
--
2.11.0
--
Michal Hocko
SUSE Labs
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