From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 2/2] timer: really raise softirq if there is irq_work to do Date: Fri, 31 Jan 2014 21:05:35 +0100 Message-ID: <20140131200535.GR5002@laptop.programming.kicks-ass.net> References: <1391178845-15837-1-git-send-email-bigeasy@linutronix.de> <1391178845-15837-2-git-send-email-bigeasy@linutronix.de> <20140131120757.594e24d6@gandalf.local.home> <20140131174227.GN9012@linux.vnet.ibm.com> <20140131125719.73340f6e@gandalf.local.home> <52EBF8FE.3080608@linutronix.de> <20140131143441.478f79ee@gandalf.local.home> <52EBFE1D.4020201@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Steven Rostedt , paulmck@linux.vnet.ibm.com, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, Clark Williams To: Sebastian Andrzej Siewior Return-path: Content-Disposition: inline In-Reply-To: <52EBFE1D.4020201@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Fri, Jan 31, 2014 at 08:48:45PM +0100, Sebastian Andrzej Siewior wrote: > > How "bad" is it? Is this something generic or just not getting > perf events fast enough out? Most users don't seem to require small > latencies. I have vague memories of there being an actual perf problem if there's a hole between the NMI/IRQ triggering the irq_work and the interrupt running the work. I should have some notes on it somewhere and an todo entry to plug the hole. But note that the MCE code also uses irq_work, they really _need_ to be fast because the system might be crumbling under their feet.