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From: Pavel Machek <pavel@ucw.cz>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: linux-mm@kvack.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, aarcange@redhat.com,
	aaron.lu@intel.com, akpm@linux-foundation.org,
	alex.williamson@redhat.com, bsd@redhat.com,
	darrick.wong@oracle.com, dave.hansen@linux.intel.com,
	jgg@mellanox.com, jwadams@google.com, jiangshanlai@gmail.com,
	mhocko@kernel.org, mike.kravetz@oracle.com,
	Pavel.Tatashin@microsoft.com, prasad.singamsetty@oracle.com,
	rdunlap@infradead.org, steven.sistare@oracle.com,
	tim.c.chen@intel.com, tj@kernel.org, vbabka@suse.cz
Subject: Re: [RFC PATCH v4 01/13] ktask: add documentation
Date: Tue, 27 Nov 2018 20:50:08 +0100
Message-ID: <20181127195008.GA20692@amd> (raw)
In-Reply-To: <20181105165558.11698-2-daniel.m.jordan@oracle.com>


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Hi!

> Motivates and explains the ktask API for kernel clients.
> 
> Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> ---
>  Documentation/core-api/index.rst |   1 +
>  Documentation/core-api/ktask.rst | 213 +++++++++++++++++++++++++++++++
>  2 files changed, 214 insertions(+)
>  create mode 100644 Documentation/core-api/ktask.rst
> 
> diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
> index 3adee82be311..c143a280a5b1 100644
> --- a/Documentation/core-api/index.rst
> +++ b/Documentation/core-api/index.rst
> @@ -18,6 +18,7 @@ Core utilities
>     refcount-vs-atomic
>     cpu_hotplug
>     idr
> +   ktask
>     local_ops
>     workqueue
>     genericirq
> diff --git a/Documentation/core-api/ktask.rst b/Documentation/core-api/ktask.rst
> new file mode 100644
> index 000000000000..c3c00e1f802f
> --- /dev/null
> +++ b/Documentation/core-api/ktask.rst
> @@ -0,0 +1,213 @@
> +.. SPDX-License-Identifier: GPL-2.0+
> +
> +============================================
> +ktask: parallelize CPU-intensive kernel work
> +============================================
> +
> +:Date: November, 2018
> +:Author: Daniel Jordan <daniel.m.jordan@oracle.com>


> +For example, consider the task of clearing a gigantic page.  This used to be
> +done in a single thread with a for loop that calls a page clearing function for
> +each constituent base page.  To parallelize with ktask, the client first moves
> +the for loop to the thread function, adapting it to operate on the range passed
> +to the function.  In this simple case, the thread function's start and end
> +arguments are just addresses delimiting the portion of the gigantic page to
> +clear.  Then, where the for loop used to be, the client calls into ktask with
> +the start address of the gigantic page, the total size of the gigantic page,
> +and the thread function.  Internally, ktask will divide the address range into
> +an appropriate number of chunks and start an appropriate number of threads to
> +complete these chunks.

Great, so my little task is bound to CPUs 1-4 and uses gigantic
pages. Kernel clears them for me.

a) Do all the CPUs work for me, or just CPUs I was assigned to?

b) Will my time my_little_task show the system time including the
worker threads?

Best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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  parent 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 [this message]
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
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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