From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: axboe@kernel.org, fweisbec@redhat.com, mingo@kernel.org,
linux-kernel@vger.kernel.org, lcapitulino@redhat.com,
mtosatti@redhat.com
Subject: Re: [PATCH RFC] nohz,blk-mq: do not create blk-mq workqueues on nohz dedicated CPUs
Date: Sun, 05 Apr 2015 07:31:59 +0200 [thread overview]
Message-ID: <1428211919.2324.23.camel@gmail.com> (raw)
In-Reply-To: <20150331102726.076a6860@annuminas.surriel.com>
On Tue, 2015-03-31 at 10:27 -0400, Rik van Riel wrote:
> CPUs with nohz_full do not want disruption from timer interrupts,
> or other random system things. This includes block mq work.
>
> There is another issue with block mq vs. realtime tasks that run
> 100% of the time, which is not uncommon on systems that have CPUs
> dedicated to real time use with isolcpus= and nohz_full=
>
> Specifically, on systems like that, a block work item may never
> get to run, which could lead to filesystems getting stuck forever.
What reason is there to run a compute hog as RT if it's the only task
on an isolated core? In an RT kernel, PI may be a reason, but if a
task is so critical that it needs bare metal, it had better not be.
-Mike
prev parent reply other threads:[~2015-04-05 5:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-31 14:27 [PATCH RFC] nohz,blk-mq: do not create blk-mq workqueues on nohz dedicated CPUs Rik van Riel
2015-03-31 15:02 ` Frederic Weisbecker
2015-03-31 23:18 ` Marcelo Tosatti
2015-04-07 13:14 ` Luiz Capitulino
2015-03-31 15:07 ` Jens Axboe
2015-03-31 15:33 ` Frederic Weisbecker
2015-03-31 15:43 ` Jens Axboe
2015-04-01 16:12 ` Rik van Riel
2015-04-03 1:15 ` Jens Axboe
2015-03-31 23:17 ` Marcelo Tosatti
2015-04-01 14:36 ` Jens Axboe
2015-04-01 14:45 ` Rik van Riel
2015-04-01 14:46 ` Jens Axboe
2015-04-05 5:31 ` Mike Galbraith [this message]
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