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From: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>
To: 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>
Cc: "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>,
	"Pavel.Tatashin@microsoft.com" <Pavel.Tatashin@microsoft.com>,
	"prasad.singamsetty@oracle.com" <prasad.singamsetty@oracle.com>,
	"rdunlap@infradead.org" <rdunlap@infradead.org>,
	"steven.sistare@ora
Subject: RE: [RFC PATCH v4 11/13] mm: parallelize deferred struct page initialization within each node
Date: Sat, 10 Nov 2018 03:48:14 +0000
Message-ID: <AT5PR8401MB1169798EBEF1EE5EBA3ABFFFABC70@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20181105165558.11698-12-daniel.m.jordan@oracle.com>

> -----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/


> 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.

---
Robert Elliott, HPE Persistent Memory

  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) [this message]
2018-11-12 16:54     ` Daniel Jordan
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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