From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Fri, 12 Jul 2002 18:47:36 +0000 Subject: Re: [Linux-ia64] Re: switch_mm race condition with Ingo's scheduler Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Fri, 12 Jul 2002 11:02:25 -0700, Grant Grundler said: Grant> Would "lazy TLB flushing" be possible? Grant> ie flush TLB of given taskid first time task needs to run on a CPU. Grant> Deal with the TLB flushing when running the task, Grant> not when creating or rescheduling to a different CPU. There is no good way to distinguish between "running a task for the first time on a CPU" and "rescheduling". It could be done, but I don't think it's worth the complexity. The overhead of checking for a delayed flush is just one load from a CPU-local variable and a test. That's in the noise compared to a context-switch. Grant> I'm thinking broadcasting TLB flushes (or IPI for that Grant> effect) is, uhm, less than optimal for scalability. But I'm Grant> no expert on CPU TLB issues. There might be lots of evils Grant> with this approach. I need to read the section on process Grant> creation/scheduling in the IA64 Linux book. (ie you don't Grant> need to explain what the book already says). With Erich's patch, there are no IPIs on wrap-around. That was the whole point of the patch (to avoid deadlock conditions). --david