From: Tejun Heo <htejun@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Matt Fleming <matt@console-pimps.org>,
Oleg Nesterov <oleg@redhat.com>,
linux-kernel@vger.kernel.org, Tony Luck <tony.luck@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
akpm@linux-foundation.org, torvalds@linux-foundation.org
Subject: Re: [RFC][PATCH 0/5] Signal scalability series
Date: Sun, 2 Oct 2011 18:38:55 -0700 [thread overview]
Message-ID: <20111003013855.GG31799@mtj.dyndns.org> (raw)
In-Reply-To: <1317474209.12973.15.camel@twins>
Hello,
(cc'ing Andrew and Linus)
On Sat, Oct 01, 2011 at 03:03:29PM +0200, Peter Zijlstra wrote:
> On Sat, 2011-10-01 at 11:16 +0100, Matt Fleming wrote:
> > I also think Thomas/Peter mentioned something about latency in
> > delivering timer signals because of contention on the per-process
> > siglock. They might have some more details on that.
>
> Right, so signal delivery is O(nr_threads), which precludes being able
> to deliver signals from hardirq context, leading to lots of ugly in -rt.
Signal delivery is O(#threads)? Delivery of fatal signal is of course
but where do we walk all threads during non-fatal signal deliveries?
What am I missing?
> Breaking up the multitude of uses of siglock certainly seems worthwhile
> esp. if it also allows for a cleanup of the horrid mess called
> signal_struct (which really should be called process_struct or so).
>
> And yes, aside from that the siglock can be quite contended because its
> pretty much the one lock serializing all of the process wide state.
Hmmm... can you please be a bit more specific? I personally has never
seen a case where siglock becomes a problem and IIUC Matt also doesn't
have actual use case at hand. Given the fragile nature of this part
of kernel, it would be nice to know what the return is.
Thank you.
--
tejun
next prev parent reply other threads:[~2011-10-03 1:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-30 15:12 Matt Fleming
2011-09-30 15:12 ` [RFC][PATCH 1/5] signal: Document signal locking rules Matt Fleming
2011-09-30 15:12 ` [RFC][PATCH 2/5] signal: Add rwlock to protect sighand->action Matt Fleming
2011-09-30 15:25 ` Peter Zijlstra
2011-09-30 15:56 ` Matt Fleming
2011-09-30 15:12 ` [RFC][PATCH 3/5] signal: Reduce sighand->siglock hold time in get_signal_to_deliver() Matt Fleming
2011-09-30 15:12 ` [RFC][PATCH 4/5] signal: Add signal->ctrl_lock for job control Matt Fleming
2011-09-30 15:30 ` Peter Zijlstra
2011-09-30 15:36 ` Matt Fleming
2011-09-30 15:12 ` [RFC][PATCH 5/5] signal: Split siglock into shared_siglock and per-thread siglock Matt Fleming
2011-09-30 16:52 ` [RFC][PATCH 0/5] Signal scalability series Oleg Nesterov
2011-09-30 18:54 ` Oleg Nesterov
2011-09-30 20:00 ` Matt Fleming
2011-09-30 23:56 ` Tejun Heo
2011-10-01 10:16 ` Matt Fleming
2011-10-01 13:03 ` Peter Zijlstra
2011-10-03 1:38 ` Tejun Heo [this message]
2011-10-03 13:56 ` Thomas Gleixner
2011-10-04 7:37 ` Tejun Heo
2011-10-03 13:07 ` Oleg Nesterov
2011-10-03 15:22 ` Peter Zijlstra
2011-10-04 17:14 ` Oleg Nesterov
2011-10-04 17:52 ` Oleg Nesterov
2011-10-04 17:54 ` Linus Torvalds
2011-10-04 18:13 ` Oleg Nesterov
2011-10-03 13:16 ` Oleg Nesterov
2011-10-04 8:56 ` Matt Fleming
2011-10-04 17:29 ` Oleg Nesterov
2011-09-30 22:30 ` Andi Kleen
2011-10-01 9:35 ` Matt Fleming
2011-10-03 15:28 ` Linus Torvalds
2011-10-03 15:43 ` Matt Fleming
2011-10-03 16:35 ` Oleg Nesterov
2011-10-03 20:58 ` Matt Fleming
2011-10-03 21:45 ` Linus Torvalds
2011-10-03 22:13 ` Thomas Gleixner
2011-10-04 8:20 ` Matt Fleming
2011-10-04 17:39 ` Oleg Nesterov
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