From: Mel Gorman <mgorman@techsingularity.net>
To: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Hillf Danton <hillf.zj@alibaba-inc.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Petr Mladek <pmladek@suse.cz>
Subject: Re: [PATCH 3/4] mm, page_alloc: Drain per-cpu pages from workqueue context
Date: Mon, 23 Jan 2017 20:04:12 +0000 [thread overview]
Message-ID: <20170123200412.mkesardc4mckk6df@techsingularity.net> (raw)
In-Reply-To: <20170123170329.GA7820@htj.duckdns.org>
On Mon, Jan 23, 2017 at 12:03:29PM -0500, Tejun Heo wrote:
> Hello,
>
> On Fri, Jan 20, 2017 at 03:26:06PM +0000, Mel Gorman wrote:
> > > This translates to queue_work_on(), which has the comment of "We queue
> > > the work to a specific CPU, the caller must ensure it can't go away.",
> > > so is this safe? lru_add_drain_all() uses get_online_cpus() around this.
> > >
> >
> > get_online_cpus() would be required.
>
> This part of workqueue usage has always been a bit clunky and I should
> imrpove it but you don't necessarily have to pin the cpus from
> queueing to execution. You can queue without checking whether the CPU
> is online and instead synchronize the actual work item execution
> against cpu offline callback so that if the work item gets executed
> after offline callback is finished, it becomes a noop.
>
What is the actual mechanism that does that? It's not something that
schedule_on_each_cpu does and one would expect that the core workqueue
implementation would get this sort of detail correct. Or is this a proposal
on how it should be done?
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2017-01-23 20:04 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-17 9:29 [PATCH 0/4] Use per-cpu allocator for !irq requests and prepare for a bulk allocator v4 Mel Gorman
2017-01-17 9:29 ` [PATCH 1/4] mm, page_alloc: Split buffered_rmqueue Mel Gorman
2017-01-17 18:07 ` Jesper Dangaard Brouer
2017-01-17 18:17 ` Vlastimil Babka
2017-01-17 20:20 ` Mel Gorman
2017-01-17 21:07 ` Mel Gorman
2017-01-17 21:24 ` Vlastimil Babka
2017-01-17 9:29 ` [PATCH 2/4] mm, page_alloc: Split alloc_pages_nodemask Mel Gorman
2017-01-17 9:29 ` [PATCH 3/4] mm, page_alloc: Drain per-cpu pages from workqueue context Mel Gorman
2017-01-20 14:26 ` Vlastimil Babka
2017-01-20 15:26 ` Mel Gorman
2017-01-23 16:29 ` Petr Mladek
2017-01-23 16:50 ` Mel Gorman
2017-01-23 17:03 ` Tejun Heo
2017-01-23 20:04 ` Mel Gorman [this message]
2017-01-23 20:55 ` Tejun Heo
2017-01-23 23:04 ` Mel Gorman
2017-01-24 16:07 ` Tejun Heo
2017-01-24 23:54 ` Mel Gorman
2017-01-25 2:02 ` Tejun Heo
2017-01-25 8:30 ` Mel Gorman
2017-01-24 11:08 ` Vlastimil Babka
2017-01-17 9:29 ` [PATCH 4/4] mm, page_alloc: Only use per-cpu allocator for irq-safe requests Mel Gorman
2017-01-20 15:02 ` Vlastimil Babka
2017-01-23 11:17 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2017-01-23 15:39 [PATCH 0/4] Use per-cpu allocator for !irq requests and prepare for a bulk allocator v5 Mel Gorman
2017-01-23 15:39 ` [PATCH 3/4] mm, page_alloc: Drain per-cpu pages from workqueue context Mel Gorman
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