From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrea Arcangeli <aarcange@redhat.com>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Hugh Dickins <hughd@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>, Hillf Danton <dhillf@gmail.com>,
David Rientjes <rientjes@google.com>,
Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
Alex Shi <lkml.alex@gmail.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] Automatic NUMA Balancing V11
Date: Mon, 17 Dec 2012 11:10:44 +0100 [thread overview]
Message-ID: <20121217101044.GA1426@gmail.com> (raw)
In-Reply-To: <CA+55aFzedbhcuo-WObUjigrXGuG2VGLqDOvh_HFA9Cn_BRkwjQ@mail.gmail.com>
* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Wed, Dec 12, 2012 at 2:03 AM, Mel Gorman <mgorman@suse.de> wrote:
> > This is a pull request for "Automatic NUMA Balancing V11". The list
>
> Ok, guys, I've pulled this and pushed out. There were some
> conflicts with both the VM changes and with the scheduler
> tree, but they were pretty small and looked simple, so I fixed
> them up and hope they all work.
Cool, thanks Linus!
> Has anybody tested the impact on single-node systems? If
> distros enable this by default (and it does have 'default y',
> which is a big no-no for new features - I undid that part)
Yes, that was for easy testing, leaving it in was an oversight.
> then there will be tons of people running this without
> actually having multiple sockets. Does it gracefully avoid
> pointless overheads for this case?
Yes. We have:
+ bool numabalancing_default = false;
+
+ if (IS_ENABLED(CONFIG_NUMA_BALANCING_DEFAULT_ENABLED))
+ numabalancing_default = true;
+
+ if (nr_node_ids > 1 && !numabalancing_override) {
+ printk(KERN_INFO "Enabling automatic NUMA balancing. "
+ "Configure with numa_balancing= or sysctl");
+ set_numabalancing_state(numabalancing_default);
+ }
The nr_node_ids check makes sure that on single-node systems we
don't enable the feature.
At that point it will be some extra passive code in the kernel -
last I measured it was around +20K to the kernel image plus a
couple of extra branches in a couple of generic paths - but no
measurable runtime overhead.
Any other negative impact would either come from preparatory or
scalability patches attached to the NUMA balancing feature,
which would be a regression we want to fix.
> Anyway, hopefully we'll have a more real numa balancing for
> 3.9, and this is still considered a reasonable base for that
> work.
We are working on it ;-)
Thanks,
Ingo
next prev parent reply other threads:[~2012-12-17 10:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 10:03 [GIT PULL] Automatic NUMA Balancing V11 Mel Gorman
2012-12-12 21:27 ` Stephen Rothwell
2012-12-12 22:17 ` Mel Gorman
2012-12-16 23:19 ` Linus Torvalds
2012-12-17 2:53 ` Hugh Dickins
2012-12-17 2:56 ` [PATCH] mm: fix kernel BUG at huge_memory.c:1474! Hugh Dickins
2012-12-17 3:00 ` Linus Torvalds
2012-12-17 10:10 ` Ingo Molnar [this message]
2012-12-17 11:12 ` [GIT PULL] Automatic NUMA Balancing V11 Mel Gorman
2012-12-17 14:05 ` [PATCH] sched: numa: Fix build error if CONFIG_NUMA_BALANCING && !CONFIG_TRANSPARENT_HUGEPAGE Mel Gorman
2012-12-18 7:55 ` David Rientjes
2012-12-18 8:03 ` [patch] x86, paravirt: fix build error when thp is disabled David Rientjes
2012-12-20 13:50 ` [GIT PULL] Automatic NUMA Balancing V11 Alex Shi
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