From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederic Weisbecker Date: Wed, 14 Apr 2010 15:29:13 +0000 Subject: Re: [PATCH 7/7] sparc64: Add function graph tracer support. Message-Id: <20100414152911.GE5142@nowhere> List-Id: References: <20100412.234300.212396783.davem@davemloft.net> In-Reply-To: <20100412.234300.212396783.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: sparclinux@vger.kernel.org On Wed, Apr 14, 2010 at 02:04:49AM -0700, David Miller wrote: > From: David Miller > Date: Tue, 13 Apr 2010 18:59:31 -0700 (PDT) > > > From: David Miller > > Date: Tue, 13 Apr 2010 16:56:39 -0700 (PDT) > > > >> I'll dig further. > > > > Ok Frederic, I think I figured it out. We only save 128 bytes > > of stack space in the mcount stubs, but that's not enough. > > Ok, one more fix after this one. > > The other problem I seem to be hitting is that we overrun the main > kernel stack with tracing enabled. > > Let's run NMIs on the hardirq stack to abate this problem for now, > patch below which I'll also push to sparc-2.6 > > The only remaining issue I have is that one of the cpus can get stuck > in the scheduler load balancer. Whatever NOHZ cpu gets selected to > balance idle domains can get stuck because the time it takes to > rebalance domains with tracing enabled exceeds the interval of the > scheduler tick, so it just balances endlessly and never makes any > forward progress from the initial timer interrupt. I observed the same thing yesterday, cpu 0 was stuck in the balancing path. Anyway, I'm testing your patches.