From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm, numa: Really disable NUMA balancing by default on single node machines
Date: Wed, 13 May 2015 09:07:46 -0400 [thread overview]
Message-ID: <55534CA2.7030105@redhat.com> (raw)
In-Reply-To: <20150513081053.GQ2462@suse.de>
On 05/13/2015 04:10 AM, Mel Gorman wrote:
> NUMA balancing is meant to be disabled by default on UMA machines but
> the check is using nr_node_ids (highest node) instead of num_online_nodes
> (online nodes). The consequences are that a UMA machine with a node ID of 1
> or higher will enable NUMA balancing. This will incur useless overhead due
> to minor faults with the impact depending on the workload. These are the
> impact on the stats when running a kernel build on a single node machine
> whose node ID happened to be 1;
>
> vanilla patched
> NUMA base PTE updates 5113158 0
> NUMA huge PMD updates 643 0
> NUMA page range updates 5442374 0
> NUMA hint faults 2109622 0
> NUMA hint local faults 2109622 0
> NUMA hint local percent 100 100
> NUMA pages migrated 0 0
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Cc: <stable@vger.kernel.org> #v3.8+
Reviewed-by: Rik van Riel <riel@redhat.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm, numa: Really disable NUMA balancing by default on single node machines
Date: Wed, 13 May 2015 09:07:46 -0400 [thread overview]
Message-ID: <55534CA2.7030105@redhat.com> (raw)
In-Reply-To: <20150513081053.GQ2462@suse.de>
On 05/13/2015 04:10 AM, Mel Gorman wrote:
> NUMA balancing is meant to be disabled by default on UMA machines but
> the check is using nr_node_ids (highest node) instead of num_online_nodes
> (online nodes). The consequences are that a UMA machine with a node ID of 1
> or higher will enable NUMA balancing. This will incur useless overhead due
> to minor faults with the impact depending on the workload. These are the
> impact on the stats when running a kernel build on a single node machine
> whose node ID happened to be 1;
>
> vanilla patched
> NUMA base PTE updates 5113158 0
> NUMA huge PMD updates 643 0
> NUMA page range updates 5442374 0
> NUMA hint faults 2109622 0
> NUMA hint local faults 2109622 0
> NUMA hint local percent 100 100
> NUMA pages migrated 0 0
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
> Cc: <stable@vger.kernel.org> #v3.8+
Reviewed-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
next prev parent reply other threads:[~2015-05-13 13:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-13 8:10 [PATCH] mm, numa: Really disable NUMA balancing by default on single node machines Mel Gorman
2015-05-13 8:10 ` Mel Gorman
2015-05-13 13:07 ` Rik van Riel [this message]
2015-05-13 13:07 ` Rik van Riel
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