From: Mel Gorman <mgorman@techsingularity.net>
To: Barry Song <21cnbao@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Mike Galbraith <efault@gmx.de>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs
Date: Fri, 3 Dec 2021 13:27:19 +0000 [thread overview]
Message-ID: <20211203132719.GD3366@techsingularity.net> (raw)
In-Reply-To: <CAGsJ_4zigz0rs9ubPjJKn0s9FsHp6A1Gpoh+cyc=cQnnMEMgYg@mail.gmail.com>
On Sat, Dec 04, 2021 at 12:14:33AM +1300, Barry Song wrote:
> > > Hi Mel, you used to have 25% * numa_weight if node has only one LLC.
> > > for a system with 4 numa, In case sd has 2 nodes, child is 1 numa node,
> > > then nr_groups=2, num_online_nodes()=4, imb_numa_nr will be
> > > child->span_weight/2/2/4?
> > >
> > > Does this patch change the behaviour for machines whose numa equals LLC?
> > >
> >
> > Yes, it changes behaviour. Instead of a flat 25%, it takes into account
> > the number of LLCs per node and the number of nodes overall.
>
> Considering the number of nodes overall seems to be quite weird to me.
> for example, for the below machines
>
> 1P * 2DIE = 2NUMA: node1 - node0
> 2P * 2DIE = 4NUMA: node1 - node0 ------ node2 - node3
> 4P * 2DIE = 8NUMA: node1 - node0 ------ node2 - node3
> node5 - node4 ------ node6 - node7
>
> if one service pins node1 and node0 in all above configurations, it seems in all
> different machines, the app will result in different behavior.
>
The intent is to balance between LLCs across the whole machine, hence
accounting for the number of online nodes.
> the other example is:
> in a 2P machine, if one app pins the first two NUMAs, the other app pins
> the last two NUMAs, why would the num_online_nodes() matter to them?
> there is no balance requirement between the two P.
>
The previous 25% imbalance also did not take pinning into account and
the choice was somewhat arbitrary.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-12-03 13:27 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 15:18 [PATCH v3 0/2] Adjust NUMA imbalance for multiple LLCs Mel Gorman
2021-12-01 15:18 ` [PATCH 1/2] sched/fair: Use weight of SD_NUMA domain in find_busiest_group Mel Gorman
2021-12-03 8:38 ` Barry Song
2021-12-03 9:51 ` Gautham R. Shenoy
2021-12-03 10:53 ` Mel Gorman
2021-12-01 15:18 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs Mel Gorman
2021-12-03 8:15 ` Barry Song
2021-12-03 10:50 ` Mel Gorman
2021-12-03 11:14 ` Barry Song
2021-12-03 13:27 ` Mel Gorman [this message]
2021-12-04 10:40 ` Peter Zijlstra
2021-12-06 8:48 ` Gautham R. Shenoy
2021-12-06 14:51 ` Peter Zijlstra
2021-12-06 15:12 ` Mel Gorman
2021-12-09 14:23 ` Valentin Schneider
2021-12-09 15:43 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2022-02-08 9:43 [PATCH v6 0/2] Adjust NUMA imbalance for " Mel Gorman
2022-02-08 9:43 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans " Mel Gorman
2022-02-08 16:19 ` Gautham R. Shenoy
2022-02-09 5:10 ` K Prateek Nayak
2022-02-09 10:33 ` Mel Gorman
2022-02-11 19:02 ` Jirka Hladky
2022-02-14 10:27 ` Srikar Dronamraju
2022-02-14 11:03 ` Vincent Guittot
2022-02-03 14:46 [PATCH v5 0/2] Adjust NUMA imbalance for " Mel Gorman
2022-02-03 14:46 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans " Mel Gorman
2022-02-04 1:30 ` kernel test robot
2022-02-04 7:06 ` Srikar Dronamraju
2022-02-04 9:04 ` Mel Gorman
2022-02-04 15:07 ` Nayak, KPrateek (K Prateek)
2022-02-04 16:45 ` Mel Gorman
2021-12-10 9:33 [PATCH v4 0/2] Adjust NUMA imbalance for " Mel Gorman
2021-12-10 9:33 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans " Mel Gorman
2021-12-13 8:28 ` Gautham R. Shenoy
2021-12-13 13:01 ` Mel Gorman
2021-12-13 14:47 ` Gautham R. Shenoy
2021-12-15 11:52 ` Gautham R. Shenoy
2021-12-15 12:25 ` Mel Gorman
2021-12-16 18:33 ` Gautham R. Shenoy
2021-12-20 11:12 ` Mel Gorman
2021-12-21 15:03 ` Gautham R. Shenoy
2021-12-21 17:13 ` Vincent Guittot
2021-12-22 8:52 ` Jirka Hladky
2022-01-04 19:52 ` Jirka Hladky
2022-01-05 10:42 ` Mel Gorman
2022-01-05 10:49 ` Mel Gorman
2022-01-10 15:53 ` Vincent Guittot
2022-01-12 10:24 ` Mel Gorman
2021-12-17 19:54 ` Gautham R. Shenoy
2021-11-25 15:19 [PATCH 0/2] Adjust NUMA imbalance for " Mel Gorman
2021-11-25 15:19 ` [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans " Mel Gorman
2021-11-26 23:22 ` kernel test robot
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