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From: Oscar Salvador <osalvador@techadventures.net>
To: akpm@linux-foundation.org
Cc: mhocko@suse.com, dan.j.williams@intel.com, david@redhat.com,
	Pavel.Tatashin@microsoft.com, Jonathan.Cameron@huawei.com,
	yasu.isimatu@gmail.com, malat@debian.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Oscar Salvador <osalvador@suse.de>
Subject: [PATCH 0/5] Refactor node_states_check_changes_online/offline
Date: Wed, 19 Sep 2018 12:08:14 +0200	[thread overview]
Message-ID: <20180919100819.25518-1-osalvador@techadventures.net> (raw)

From: Oscar Salvador <osalvador@suse.de>

This patchset refactors/clean ups node_states_check_changes_online/offline
functions together with node_states_set/clear_node.

The main reason behind this patchset is that currently, these
functions are suboptimal and confusing.

For example, they contain wrong statements like:

if (N_MEMORY == N_NORMAL_MEMORY)
if (N_MEMORY =! N_NORMAL_MEMORY)
if (N_MEMORY != N_HIGH_MEMORY)
if (N_MEMORY == N_HIGH_MEMORY)

These comparasions are wrong, as N_MEMORY will never be equal
to either N_NORMAL_MEMORY or N_HIGH_MEMORY.
Although the statements do not "affect" the flow because in the way
they are placed, they are completely wrong and confusing.

I caught another misuse of this in [1].

Another thing that this patchset addresses is the fact that
some functions get called twice, or even unconditionally, without
any need.

Examples of this are:

- node_states_set_node()->node_set_state(node, N_MEMORY)

* node_states_set_node() gets called whenever we online pages,
  so we end up calling node_set_state(node, N_MEMORY) everytime.
  To avoid this, we should check if the node is already in
  node_state[N_MEMORY].

- node_states_set_node()->node_set_state(node, N_HIGH_MEMORY)

* On !CONFIG_HIGH_MEMORY, N_HIGH_MEMORY == N_NORMAL_MEMORY,
  but the current code sets:
  status_change_nid_high = status_change_nid_normal
  This means that we will call node_set_state(node, N_NORMAL_MEMORY) twice.
  The fix here is to set status_change_nid_normal = -1 on such systems,
  so we skip the second call.

[1] https://patchwork.kernel.org/patch/10579155/

Oscar Salvador (5):
  mm/memory_hotplug: Spare unnecessary calls to node_set_state
  mm/memory_hotplug: Avoid node_set/clear_state(N_HIGH_MEMORY) when
    !CONFIG_HIGHMEM
  mm/memory_hotplug: Tidy up node_states_clear_node
  mm/memory_hotplug: Simplify node_states_check_changes_online
  mm/memory_hotplug: Clean up node_states_check_changes_offline

 mm/memory_hotplug.c | 153 +++++++++++++++++++++-------------------------------
 1 file changed, 60 insertions(+), 93 deletions(-)

-- 
2.13.6


             reply	other threads:[~2018-09-19 10:09 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-19 10:08 Oscar Salvador [this message]
2018-09-19 10:08 ` [PATCH 1/5] mm/memory_hotplug: Spare unnecessary calls to node_set_state Oscar Salvador
2018-09-20 20:53   ` Pasha Tatashin
2018-09-19 10:08 ` [PATCH 2/5] mm/memory_hotplug: Avoid node_set/clear_state(N_HIGH_MEMORY) when !CONFIG_HIGHMEM Oscar Salvador
2018-09-20 20:59   ` Pasha Tatashin
2018-09-21 10:31     ` Oscar Salvador
2018-09-19 10:08 ` [PATCH 3/5] mm/memory_hotplug: Tidy up node_states_clear_node Oscar Salvador
2018-09-20 23:40   ` Pasha Tatashin
2018-09-19 10:08 ` [PATCH 4/5] mm/memory_hotplug: Simplify node_states_check_changes_online Oscar Salvador
2018-09-21  0:15   ` Pasha Tatashin
2018-09-21 10:30     ` Oscar Salvador
2018-09-19 10:08 ` [PATCH 5/5] mm/memory_hotplug: Clean up node_states_check_changes_offline Oscar Salvador
2018-09-21  0:38   ` Pasha Tatashin

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