From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [Qemu-devel] [RFC][PATCH] Register Linux dyntick timer as per-thread signal Date: Fri, 17 Jun 2011 11:25:23 +0200 Message-ID: <4DFB1D83.3020606@siemens.com> References: <4DF9CD7E.5020509@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: qemu-devel , Anthony Liguori , Paolo Bonzini , Sasha Levin , kvm To: Alexandre Raymond Return-path: Received: from goliath.siemens.de ([192.35.17.28]:28343 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753227Ab1FQJZg (ORCPT ); Fri, 17 Jun 2011 05:25:36 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 2011-06-16 17:24, Alexandre Raymond wrote: > Hi Jan, > > On Thu, Jun 16, 2011 at 5:31 AM, Jan Kiszka wrote: >> Ingo Molnar pointed out that sending the timer signal to the whole >> process, just blocking it everywhere, is suboptimal with an increasing >> number of threads. QEMU is using this pattern so far. > > I am not familiar with this code, but don't you already need to block > SIGALRM properly in all threads for OSes != Linux ? If so, isn't this > patch redundant? Yes, we still need to block for the sake of non-Linux UNIX or pre-signalfd Linux. That blocking becomes in fact redundant in the signalfd case, but that's both harmless and not worth optimizing. The key is that per-thread signals do not care about other threads having them blocked or not, they only deal with the target thread. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux