KVM Archive on lore.kernel.org
 help / color / Atom feed
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>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"aarcange@redhat.com" <aarcange@redhat.com>,
	"aaron.lu@intel.com" <aaron.lu@intel.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"bsd@redhat.com" <bsd@redhat.com>,
	"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"jgg@mellanox.com" <jgg@mellanox.com>,
	"jwadams@google.com" <jwadams@google.com>,
	"jiangshanlai@gmail.com" <jiangshanlai@gmail.com>,
	"mhocko@kernel.org" <mhocko@kernel.org>,
	"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
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
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.

  reply index

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181112165412.vizeiv6oimsuxkbk@ca-dmjordan1.us.oracle.com \
    --to=daniel.m.jordan@oracle.com \
    --cc=aarcange@redhat.com \
    --cc=aaron.lu@intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=alex.williamson@redhat.com \
    --cc=bsd@redhat.com \
    --cc=darrick.wong@oracle.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=elliott@hpe.com \
    --cc=jgg@mellanox.com \
    --cc=jiangshanlai@gmail.com \
    --cc=jwadams@google.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=mike.kravetz@oracle.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git