From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
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Subject: Re: [RFC PATCH v4 11/13] mm: parallelize deferred struct page initialization within each node
Date: Mon, 12 Nov 2018 08:54:12 -0800 [thread overview]
Message-ID: <20181112165412.vizeiv6oimsuxkbk@ca-dmjordan1.us.oracle.com> (raw)
In-Reply-To: <AT5PR8401MB1169798EBEF1EE5EBA3ABFFFABC70@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM>
On Sat, Nov 10, 2018 at 03:48:14AM +0000, Elliott, Robert (Persistent Memory) wrote:
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> > owner@vger.kernel.org> On Behalf Of Daniel Jordan
> > Sent: Monday, November 05, 2018 10:56 AM
> > Subject: [RFC PATCH v4 11/13] mm: parallelize deferred struct page
> > initialization within each node
> >
> > ... The kernel doesn't
> > know the memory bandwidth of a given system to get the most efficient
> > number of threads, so there's some guesswork involved.
>
> The ACPI HMAT (Heterogeneous Memory Attribute Table) is designed to report
> that kind of information, and could facilitate automatic tuning.
>
> There was discussion last year about kernel support for it:
> https://lore.kernel.org/lkml/20171214021019.13579-1-ross.zwisler@linux.intel.com/
Thanks for bringing this up. I'm traveling but will take a closer look when I
get back.
> > In testing, a reasonable value turned out to be about a quarter of the
> > CPUs on the node.
> ...
> > + /*
> > + * We'd like to know the memory bandwidth of the chip to
> > calculate the
> > + * most efficient number of threads to start, but we can't.
> > + * In testing, a good value for a variety of systems was a
> > quarter of the CPUs on the node.
> > + */
> > + nr_node_cpus = DIV_ROUND_UP(cpumask_weight(cpumask), 4);
>
>
> You might want to base that calculation on and limit the threads to
> physical cores, not hyperthreaded cores.
Why? Hyperthreads can be beneficial when waiting on memory. That said, I
don't have data that shows that in this case.
next prev parent reply other threads:[~2018-11-12 16:54 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 16:55 [RFC PATCH v4 00/13] ktask: multithread CPU-intensive kernel work Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 01/13] ktask: add documentation Daniel Jordan
2018-11-05 21:19 ` Randy Dunlap
2018-11-06 2:27 ` Daniel Jordan
2018-11-06 8:49 ` Peter Zijlstra
2018-11-06 20:34 ` Daniel Jordan
2018-11-06 20:51 ` Jason Gunthorpe
2018-11-07 10:27 ` Peter Zijlstra
2018-11-07 20:21 ` Daniel Jordan
2018-11-07 10:35 ` Peter Zijlstra
2018-11-07 21:20 ` Daniel Jordan
2018-11-08 17:26 ` Jonathan Corbet
2018-11-08 19:15 ` Daniel Jordan
2018-11-08 19:24 ` Jonathan Corbet
2018-11-27 19:50 ` Pavel Machek
2018-11-28 16:56 ` Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 02/13] ktask: multithread CPU-intensive kernel work Daniel Jordan
2018-11-05 20:51 ` Randy Dunlap
2018-11-06 2:24 ` Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 03/13] ktask: add undo support Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 04/13] ktask: run helper threads at MAX_NICE Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 05/13] workqueue, ktask: renice helper threads to prevent starvation Daniel Jordan
2018-11-13 16:34 ` Tejun Heo
2018-11-19 16:45 ` Daniel Jordan
2018-11-20 16:33 ` Tejun Heo
2018-11-20 17:03 ` Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 06/13] vfio: parallelize vfio_pin_map_dma Daniel Jordan
2018-11-05 21:51 ` Alex Williamson
2018-11-06 2:42 ` Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 07/13] mm: change locked_vm's type from unsigned long to atomic_long_t Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 08/13] vfio: remove unnecessary mmap_sem writer acquisition around locked_vm Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 09/13] vfio: relieve mmap_sem reader cacheline bouncing by holding it longer Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 10/13] mm: enlarge type of offset argument in mem_map_offset and mem_map_next Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 11/13] mm: parallelize deferred struct page initialization within each node Daniel Jordan
2018-11-10 3:48 ` Elliott, Robert (Persistent Memory)
2018-11-12 16:54 ` Daniel Jordan [this message]
2018-11-12 22:15 ` Elliott, Robert (Persistent Memory)
2018-11-19 16:01 ` Daniel Jordan
2018-11-27 0:12 ` Elliott, Robert (Persistent Memory)
2018-11-27 20:23 ` Daniel Jordan
2018-11-19 16:29 ` Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 12/13] mm: parallelize clear_gigantic_page Daniel Jordan
2018-11-05 16:55 ` [RFC PATCH v4 13/13] hugetlbfs: parallelize hugetlbfs_fallocate with ktask Daniel Jordan
2018-11-05 17:29 ` [RFC PATCH v4 00/13] ktask: multithread CPU-intensive kernel work Michal Hocko
2018-11-06 1:29 ` Daniel Jordan
2018-11-06 9:21 ` Michal Hocko
2018-11-07 20:17 ` Daniel Jordan
2018-11-05 18:49 ` Zi Yan
2018-11-06 2:20 ` Daniel Jordan
2018-11-06 2:48 ` Zi Yan
2018-11-06 19:00 ` Daniel Jordan
2018-11-30 19:18 ` Tejun Heo
2018-12-01 0:13 ` Daniel Jordan
2018-12-03 16:16 ` Tejun Heo
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