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From: Mel Gorman <mgorman@suse.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>, Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 02/63] mm: numa: Document automatic NUMA balancing sysctls
Date: Mon,  7 Oct 2013 11:28:40 +0100
Message-ID: <1381141781-10992-3-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1381141781-10992-1-git-send-email-mgorman@suse.de>

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 Documentation/sysctl/kernel.txt | 66 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 9d4c1d1..1428c66 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -355,6 +355,72 @@ utilize.
 
 ==============================================================
 
+numa_balancing
+
+Enables/disables automatic page fault based NUMA memory
+balancing. Memory is moved automatically to nodes
+that access it often.
+
+Enables/disables automatic NUMA memory balancing. On NUMA machines, there
+is a performance penalty if remote memory is accessed by a CPU. When this
+feature is enabled the kernel samples what task thread is accessing memory
+by periodically unmapping pages and later trapping a page fault. At the
+time of the page fault, it is determined if the data being accessed should
+be migrated to a local memory node.
+
+The unmapping of pages and trapping faults incur additional overhead that
+ideally is offset by improved memory locality but there is no universal
+guarantee. If the target workload is already bound to NUMA nodes then this
+feature should be disabled. Otherwise, if the system overhead from the
+feature is too high then the rate the kernel samples for NUMA hinting
+faults may be controlled by the numa_balancing_scan_period_min_ms,
+numa_balancing_scan_delay_ms, numa_balancing_scan_period_reset,
+numa_balancing_scan_period_max_ms and numa_balancing_scan_size_mb sysctls.
+
+==============================================================
+
+numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms,
+numa_balancing_scan_period_max_ms, numa_balancing_scan_period_reset,
+numa_balancing_scan_size_mb
+
+Automatic NUMA balancing scans tasks address space and unmaps pages to
+detect if pages are properly placed or if the data should be migrated to a
+memory node local to where the task is running.  Every "scan delay" the task
+scans the next "scan size" number of pages in its address space. When the
+end of the address space is reached the scanner restarts from the beginning.
+
+In combination, the "scan delay" and "scan size" determine the scan rate.
+When "scan delay" decreases, the scan rate increases.  The scan delay and
+hence the scan rate of every task is adaptive and depends on historical
+behaviour. If pages are properly placed then the scan delay increases,
+otherwise the scan delay decreases.  The "scan size" is not adaptive but
+the higher the "scan size", the higher the scan rate.
+
+Higher scan rates incur higher system overhead as page faults must be
+trapped and potentially data must be migrated. However, the higher the scan
+rate, the more quickly a tasks memory is migrated to a local node if the
+workload pattern changes and minimises performance impact due to remote
+memory accesses. These sysctls control the thresholds for scan delays and
+the number of pages scanned.
+
+numa_balancing_scan_period_min_ms is the minimum delay in milliseconds
+between scans. It effectively controls the maximum scanning rate for
+each task.
+
+numa_balancing_scan_delay_ms is the starting "scan delay" used for a task
+when it initially forks.
+
+numa_balancing_scan_period_max_ms is the maximum delay between scans. It
+effectively controls the minimum scanning rate for each task.
+
+numa_balancing_scan_size_mb is how many megabytes worth of pages are
+scanned for a given scan.
+
+numa_balancing_scan_period_reset is a blunt instrument that controls how
+often a tasks scan delay is reset to detect sudden changes in task behaviour.
+
+==============================================================
+
 osrelease, ostype & version:
 
 # cat osrelease
-- 
1.8.4

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  parent reply index

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-07 10:28 [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V9 Mel Gorman
2013-10-07 10:28 ` [PATCH 01/63] hotplug: Optimize {get,put}_online_cpus() Mel Gorman
2013-10-07 10:28 ` Mel Gorman [this message]
2013-10-07 12:46   ` [PATCH 02/63] mm: numa: Document automatic NUMA balancing sysctls Rik van Riel
2013-10-07 10:28 ` [PATCH 03/63] sched, numa: Comment fixlets Mel Gorman
2013-10-07 12:46   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 04/63] mm: numa: Do not account for a hinting fault if we raced Mel Gorman
2013-10-07 12:47   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 05/63] mm: Wait for THP migrations to complete during NUMA hinting faults Mel Gorman
2013-10-07 13:55   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 06/63] mm: Prevent parallel splits during THP migration Mel Gorman
2013-10-07 14:01   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 07/63] mm: numa: Sanitize task_numa_fault() callsites Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 08/63] mm: Close races between THP migration and PMD numa clearing Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 09/63] mm: Account for a THP NUMA hinting update as one PTE update Mel Gorman
2013-10-07 14:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 10/63] mm: Do not flush TLB during protection change if !pte_present && !migration_entry Mel Gorman
2013-10-07 15:12   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 11/63] mm: Only flush TLBs if a transhuge PMD is modified for NUMA pte scanning Mel Gorman
2013-10-07 10:28 ` [PATCH 12/63] mm: numa: Do not migrate or account for hinting faults on the zero page Mel Gorman
2013-10-07 17:10   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 13/63] sched: numa: Mitigate chance that same task always updates PTEs Mel Gorman
2013-10-07 17:24   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 14/63] sched: numa: Continue PTE scanning even if migrate rate limited Mel Gorman
2013-10-07 17:24   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 15/63] Revert "mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node" Mel Gorman
2013-10-07 17:42   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 16/63] sched: numa: Initialise numa_next_scan properly Mel Gorman
2013-10-07 17:44   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 17/63] sched: Set the scan rate proportional to the memory usage of the task being scanned Mel Gorman
2013-10-07 17:44   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 18/63] sched: numa: Slow scan rate if no NUMA hinting faults are being recorded Mel Gorman
2013-10-07 18:02   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 19/63] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-10-07 18:02   ` Rik van Riel
2013-12-04  5:32   ` Wanpeng Li
2013-12-04  5:37     ` Wanpeng Li
2013-10-07 10:28 ` [PATCH 20/63] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-10-07 18:04   ` Rik van Riel
2013-10-07 10:28 ` [PATCH 21/63] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-10-07 18:39   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 22/63] sched: Favour moving tasks towards the preferred node Mel Gorman
2013-10-07 18:39   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 23/63] sched: Resist moving tasks towards nodes with fewer hinting faults Mel Gorman
2013-10-07 18:40   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 24/63] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-10-07 18:40   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 25/63] sched: Add infrastructure for split shared/private accounting of NUMA hinting faults Mel Gorman
2013-10-07 18:41   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 26/63] sched: Check current->mm before allocating NUMA faults Mel Gorman
2013-10-07 18:41   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 27/63] mm: numa: Scan pages with elevated page_mapcount Mel Gorman
2013-10-07 18:43   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 28/63] sched: Remove check that skips small VMAs Mel Gorman
2013-10-07 18:44   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 29/63] sched: Set preferred NUMA node based on number of private faults Mel Gorman
2013-10-07 18:45   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 30/63] sched: Do not migrate memory immediately after switching node Mel Gorman
2013-10-07 10:29 ` [PATCH 31/63] mm: numa: only unmap migrate-on-fault VMAs Mel Gorman
2013-10-07 10:29 ` [PATCH 32/63] sched: Avoid overloading CPUs on a preferred NUMA node Mel Gorman
2013-10-07 18:58   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 33/63] sched: Retry migration of tasks to CPU on a preferred node Mel Gorman
2013-10-07 18:58   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 34/63] sched: numa: increment numa_migrate_seq when task runs in correct location Mel Gorman
2013-10-07 10:29 ` [PATCH 35/63] sched: numa: Do not trap hinting faults for shared libraries Mel Gorman
2013-10-07 19:04   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 36/63] mm: numa: Only trap pmd hinting faults if we would otherwise trap PTE faults Mel Gorman
2013-10-07 19:06   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 37/63] stop_machine: Introduce stop_two_cpus() Mel Gorman
2013-10-07 10:29 ` [PATCH 38/63] sched: Introduce migrate_swap() Mel Gorman
2013-10-07 19:06   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 39/63] sched: numa: Use a system-wide search to find swap/migration candidates Mel Gorman
2013-10-07 19:07   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 40/63] sched: numa: Favor placing a task on the preferred node Mel Gorman
2013-10-07 19:07   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 41/63] sched: numa: fix placement of workloads spread across multiple nodes Mel Gorman
2013-10-07 10:29 ` [PATCH 42/63] mm: numa: Change page last {nid,pid} into {cpu,pid} Mel Gorman
2013-10-07 19:08   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 43/63] sched: numa: Use {cpu, pid} to create task groups for shared faults Mel Gorman
2013-10-07 19:09   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 44/63] sched: numa: Report a NUMA task group ID Mel Gorman
2013-10-07 19:09   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 45/63] mm: numa: copy cpupid on page migration Mel Gorman
2013-10-07 10:29 ` [PATCH 46/63] mm: numa: Do not group on RO pages Mel Gorman
2013-10-07 19:10   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 47/63] mm: numa: Do not batch handle PMD pages Mel Gorman
2013-10-07 19:11   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 48/63] sched: numa: stay on the same node if CLONE_VM Mel Gorman
2013-10-07 10:29 ` [PATCH 49/63] sched: numa: use group fault statistics in numa placement Mel Gorman
2013-10-07 10:29 ` [PATCH 50/63] sched: numa: call task_numa_free from do_execve Mel Gorman
2013-10-07 10:29 ` [PATCH 51/63] sched: numa: Prevent parallel updates to group stats during placement Mel Gorman
2013-10-07 19:13   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 52/63] sched: numa: add debugging Mel Gorman
2013-10-07 19:13   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 53/63] sched: numa: Decide whether to favour task or group weights based on swap candidate relationships Mel Gorman
2013-10-07 10:29 ` [PATCH 54/63] sched: numa: fix task or group comparison Mel Gorman
2013-10-07 10:29 ` [PATCH 55/63] sched: numa: Avoid migrating tasks that are placed on their preferred node Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 56/63] sched: numa: be more careful about joining numa groups Mel Gorman
2013-10-07 10:29 ` [PATCH 57/63] sched: numa: Take false sharing into account when adapting scan rate Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 58/63] sched: numa: adjust scan rate in task_numa_placement Mel Gorman
2013-10-07 10:29 ` [PATCH 59/63] sched: numa: Remove the numa_balancing_scan_period_reset sysctl Mel Gorman
2013-10-07 19:14   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 60/63] mm: numa: revert temporarily disabling of NUMA migration Mel Gorman
2013-10-07 10:29 ` [PATCH 61/63] sched: numa: skip some page migrations after a shared fault Mel Gorman
2013-10-07 10:29 ` [PATCH 62/63] sched: numa: use unsigned longs for numa group fault stats Mel Gorman
2013-10-07 19:15   ` Rik van Riel
2013-10-07 10:29 ` [PATCH 63/63] sched: numa: periodically retry task_numa_migrate Mel Gorman
2013-10-09 11:03 ` [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V9 Ingo Molnar
2013-10-09 11:11   ` Ingo Molnar
2013-10-09 11:13     ` Ingo Molnar
2013-10-09 12:05   ` Peter Zijlstra
2013-10-09 12:48     ` Ingo Molnar
2013-10-10  7:05   ` Mel Gorman
2013-10-09 16:28 ` Ingo Molnar
2013-10-09 16:29   ` Ingo Molnar
2013-10-09 16:57     ` Ingo Molnar
2013-10-09 17:09       ` Ingo Molnar
2013-10-09 17:11         ` Peter Zijlstra
2013-10-09 17:08   ` Peter Zijlstra
2013-10-09 17:15     ` Ingo Molnar
2013-10-09 17:18       ` Peter Zijlstra
2013-10-24 12:26 ` Automatic NUMA balancing patches for tip-urgent/stable Mel Gorman
2013-10-26 12:11   ` Ingo Molnar
2013-10-29  9:42     ` Mel Gorman
2013-10-29  9:48       ` Ingo Molnar
2013-10-29 10:24         ` Mel Gorman
2013-10-29 10:41           ` Ingo Molnar
2013-10-29 12:48             ` Mel Gorman
2013-10-31  9:51   ` [RFC GIT PULL] NUMA-balancing memory corruption fixes Ingo Molnar
2013-10-31 22:25     ` Linus Torvalds
2013-11-01  7:36       ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2013-09-27 13:26 [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V8 Mel Gorman
2013-09-27 13:26 ` [PATCH 02/63] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman

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