From mboxrd@z Thu Jan 1 00:00:00 1970 From: a.p.zijlstra@chello.nl (Peter Zijlstra) Date: Thu, 11 Nov 2010 13:06:16 +0100 Subject: [Questions] How to run 'perf top' on ARM to profile kernel functions with modules loaded In-Reply-To: <20101111091733.GA2929@pulham.picochip.com> References: <20101111091733.GA2929@pulham.picochip.com> Message-ID: <1289477176.2084.64.camel@laptop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 2010-11-11 at 09:17 +0000, Jamie Iles wrote: > On Thu, Nov 11, 2010 at 03:52:07PM +0800, Ming Lei wrote: > > 2010/11/11 Ming Lei : > > > Hi, > > > > > > 'perf top' can't display any functions when modules are loaded on ARM. > > > > Sorry, should be can't display any kernel functions when modules are loaded > > on ARM. > I've noticed this myself and I spent a bit of time looking into it last week > but didn't get too far. I did wonder if it was something to do with the map > fixups after loading the modules. If you look at the raw events after a perf > record with 'perf report -D' then the last module has a size that takes it to > 0xFFFFFFFF which overlaps with the rest of the kernel symbols. > > On x86 it looks like the modules are loaded after the kernel image in VM > unlike ARM. Order shouldn't matter, but that overlap is very likely what kills it. That module size is buggy.