From: Andi Kleen <andi@firstfloor.org>
To: Ivo Sieben <meltedpianoman@gmail.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-serial@vger.kernel.org, Alan Cox <alan@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [REPOST] RFC: sched: Prevent wakeup to enter critical section needlessly
Date: Tue, 09 Oct 2012 06:37:27 -0700 [thread overview]
Message-ID: <m2r4p7u5pk.fsf@firstfloor.org> (raw)
In-Reply-To: <1349782235-8896-1-git-send-email-meltedpianoman@gmail.com> (Ivo Sieben's message of "Tue, 9 Oct 2012 13:30:35 +0200")
Ivo Sieben <meltedpianoman@gmail.com> writes:
> Check the waitqueue task list to be non empty before entering the critical
> section. This prevents locking the spin lock needlessly in case the queue
> was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
> system.
>
> Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com>
> ---
>
> REPOST:
> Request for comments:
> - Does this make any sense?
Looks good to me. Avoiding any spinlock is good. I don't even think you
need "careful", if you miss an update it was just as it happened a
little later.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Ivo Sieben <meltedpianoman@gmail.com>
Cc: <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
<linux-serial@vger.kernel.org>, Alan Cox <alan@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [REPOST] RFC: sched: Prevent wakeup to enter critical section needlessly
Date: Tue, 09 Oct 2012 06:37:27 -0700 [thread overview]
Message-ID: <m2r4p7u5pk.fsf@firstfloor.org> (raw)
In-Reply-To: <1349782235-8896-1-git-send-email-meltedpianoman@gmail.com> (Ivo Sieben's message of "Tue, 9 Oct 2012 13:30:35 +0200")
Ivo Sieben <meltedpianoman@gmail.com> writes:
> Check the waitqueue task list to be non empty before entering the critical
> section. This prevents locking the spin lock needlessly in case the queue
> was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
> system.
>
> Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com>
> ---
>
> REPOST:
> Request for comments:
> - Does this make any sense?
Looks good to me. Avoiding any spinlock is good. I don't even think you
need "careful", if you miss an update it was just as it happened a
little later.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2012-10-09 13:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-24 13:06 [PATCH] RFC: sched: Prevent wakeup to enter critical section needlessly Ivo Sieben
2012-09-24 13:06 ` Ivo Sieben
2012-10-09 11:30 ` [REPOST] " Ivo Sieben
2012-10-09 11:30 ` Ivo Sieben
2012-10-09 13:37 ` Andi Kleen [this message]
2012-10-09 13:37 ` Andi Kleen
2012-10-09 14:15 ` Peter Zijlstra
2012-10-09 15:17 ` Oleg Nesterov
2012-10-10 14:02 ` Andi Kleen
2012-10-18 8:30 ` [PATCH-v2] " Ivo Sieben
2012-10-18 8:30 ` Ivo Sieben
2012-10-25 10:12 ` [REPOST-v2] " Ivo Sieben
2012-10-25 10:12 ` Ivo Sieben
2012-11-19 7:30 ` Ivo Sieben
2012-11-19 7:30 ` Ivo Sieben
2012-11-19 10:20 ` Preeti U Murthy
2012-11-19 15:10 ` Oleg Nesterov
2012-11-19 15:34 ` Ivo Sieben
2012-11-19 15:49 ` Oleg Nesterov
2012-11-21 13:03 ` Ivo Sieben
2012-11-21 13:47 ` Alan Cox
2012-11-21 13:58 ` Oleg Nesterov
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