From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Dave Jones <davej@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Oleg Nesterov <oleg@redhat.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 2/3] context_tracking: Inherit TIF_NOHZ through forks instead of context switches
Date: Thu, 2 Apr 2015 21:09:10 +0200 [thread overview]
Message-ID: <20150402190910.GF27490@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1427996365-12101-3-git-send-email-fweisbec@gmail.com>
On Thu, Apr 02, 2015 at 07:39:24PM +0200, Frederic Weisbecker wrote:
> TIF_NOHZ is used by context_tracking to force syscall slow-path on every
> task in order to track userspace roundtrips. As such, it must be set on
> all running tasks.
>
> It's currently explicitly inherited through context switches. There is
> no need to do it on this fast-path though. The flag could be simply
> set once for all on all tasks, whether they are running or not.
>
> Lets do this by setting the flag to init task on early boot and let it
> propagate through fork inheritance.
>
One must ask, what's the point of the flag if everybody must always have
it set?
next prev parent reply other threads:[~2015-04-02 19:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-02 17:39 [PATCH 0/3] context_tracking: A few improvements Frederic Weisbecker
2015-04-02 17:39 ` [PATCH 1/3] context_tracking: Protect against recursion Frederic Weisbecker
2015-04-02 18:01 ` Rik van Riel
2015-04-02 17:39 ` [PATCH 2/3] context_tracking: Inherit TIF_NOHZ through forks instead of context switches Frederic Weisbecker
2015-04-02 18:06 ` Rik van Riel
2015-04-02 18:08 ` Oleg Nesterov
2015-04-03 17:19 ` Frederic Weisbecker
2015-04-02 19:09 ` Peter Zijlstra [this message]
2015-04-02 19:11 ` Rik van Riel
2015-04-03 17:21 ` Frederic Weisbecker
2015-04-02 19:19 ` Oleg Nesterov
2015-04-02 17:39 ` [PATCH 3/3] context_tracking: Tag init code Frederic Weisbecker
2015-04-02 18:07 ` Rik van Riel
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