From: Byungchul Park <byungchul.park@lge.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Juri Lelli <juri.lelli@arm.com>,
peterz@infradead.org, mingo@kernel.org,
linux-kernel@vger.kernel.org, juri.lelli@gmail.com,
bristot@redhat.com, kernel-team@lge.com
Subject: Re: [PATCH v4 1/5] sched/deadline: Refer to cpudl.elements atomically
Date: Tue, 23 May 2017 10:11:23 +0900 [thread overview]
Message-ID: <20170523011123.GH28017@X58A-UD3R> (raw)
In-Reply-To: <20170516091053.5f0868b5@gandalf.local.home>
On Tue, May 16, 2017 at 09:10:53AM -0400, Steven Rostedt wrote:
> On Tue, 16 May 2017 11:32:41 +0100
> Juri Lelli <juri.lelli@arm.com> wrote:
>
>
> > Not sure, but if we are going to retry a lot it might be better off to
> > put proper locking instead? We could also simply bail out when we notice
>
> Actually, locking can make it much worse. I've been playing with RT on
> boxes with 240 cores (with HT turned off!), and *any* locks in the
> scheduler can cause huge contention.
OK. I give up patches adding locks here. Thank you for explaning why you
did not write code in such a way like mine.
> > that something is changed under our feet. I'd say (again :) we might
> > first want to understand (with some numbers) how bad the problem is and
> > then fix it. I guess numbers might also help us to better understand
> > what the best fix is?
>
> Exactly. I haven't seen any numbers. Yes, it is not perfect, but we
> don't know how unperfect it is. Numbers will help to know if there is
> even a problem or not with the current solution.
Yes. I am also curious about the number and want to check the number,
but it's not easy to me since I don't have such a big machine. For now,
only thing I can do is to skip the patch.
Thank you very much for all of your opinions.
next prev parent reply other threads:[~2017-05-23 1:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-12 5:48 [PATCH v4 0/5] Make find_later_rq() choose a closer cpu in topology Byungchul Park
2017-05-12 5:48 ` [PATCH v4 1/5] sched/deadline: Refer to cpudl.elements atomically Byungchul Park
2017-05-12 14:25 ` Steven Rostedt
2017-05-15 8:36 ` Juri Lelli
2017-05-16 7:00 ` Byungchul Park
2017-05-16 6:52 ` Byungchul Park
2017-05-16 10:32 ` Juri Lelli
2017-05-16 13:10 ` Steven Rostedt
2017-05-23 1:11 ` Byungchul Park [this message]
2017-05-12 5:48 ` [PATCH v4 2/5] sched/deadline: Make find_later_rq() choose a closer cpu in topology Byungchul Park
2017-05-12 5:48 ` [PATCH v4 3/5] sched/deadline: Change return value of cpudl_find() Byungchul Park
2017-05-12 5:48 ` [PATCH v4 4/5] sched/deadline: Add support for SD_PREFER_SIBLING on find_later_rq() Byungchul Park
2017-05-12 5:48 ` [PATCH v4 5/5] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq() Byungchul Park
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