From: Tejun Heo <tj@kernel.org>
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, vbabka@suse.cz
Subject: Re: [RFC PATCH v4 05/13] workqueue, ktask: renice helper threads to prevent starvation
Date: Tue, 13 Nov 2018 08:34:00 -0800 [thread overview]
Message-ID: <20181113163400.GK2509588@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <20181105165558.11698-6-daniel.m.jordan@oracle.com>
Hello, Daniel.
On Mon, Nov 05, 2018 at 11:55:50AM -0500, Daniel Jordan wrote:
> static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
> - bool from_cancel)
> + struct nice_work *nice_work, int flags)
> {
> struct worker *worker = NULL;
> struct worker_pool *pool;
> @@ -2868,11 +2926,19 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
> if (pwq) {
> if (unlikely(pwq->pool != pool))
> goto already_gone;
> +
> + /* not yet started, insert linked work before work */
> + if (unlikely(flags & WORK_FLUSH_AT_NICE))
> + insert_nice_work(pwq, nice_work, work);
So, I'm not sure this works that well. e.g. what if the work item is
waiting for other work items which are at lower priority? Also, in
this case, it'd be a lot simpler to simply dequeue the work item and
execute it synchronously.
> } else {
> worker = find_worker_executing_work(pool, work);
> if (!worker)
> goto already_gone;
> pwq = worker->current_pwq;
> + if (unlikely(flags & WORK_FLUSH_AT_NICE)) {
> + set_user_nice(worker->task, nice_work->nice);
> + worker->flags |= WORKER_NICED;
> + }
> }
I'm not sure about this. Can you see whether canceling & executing
synchronously is enough to address the latency regression?
Thanks.
--
tejun
next prev parent reply other threads:[~2018-11-13 16:34 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 [this message]
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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