From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753852AbbAZM3d (ORCPT ); Mon, 26 Jan 2015 07:29:33 -0500 Received: from mail.kernel.org ([198.145.29.136]:33556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595AbbAZM33 (ORCPT ); Mon, 26 Jan 2015 07:29:29 -0500 Date: Mon, 26 Jan 2015 09:29:32 -0300 From: Arnaldo Carvalho de Melo To: Will Deacon Cc: Russell King - ARM Linux , Felipe Balbi , Peter Zijlstra , Tony Lindgren , Linux Kernel Mailing List , Ingo Molnar , Paul Mackerras , Linux OMAP Mailing List , Linux ARM Kernel Mailing List Subject: Re: perf not capturing stack traces Message-ID: <20150126122932.GB16629@kernel.org> References: <20150123195128.GE26557@saruman.tx.rr.com> <20150123205959.GD3073@kernel.org> <20150123223745.GJ26557@saruman.tx.rr.com> <20150124151204.GF3073@kernel.org> <20150124222342.GA26941@saruman.tx.rr.com> <20150125155651.GB11502@n2100.arm.linux.org.uk> <20150126102711.GC15598@arm.com> <20150126121243.GA16629@kernel.org> <20150126121621.GG15598@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150126121621.GG15598@arm.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Mon, Jan 26, 2015 at 12:16:21PM +0000, Will Deacon escreveu: > On Mon, Jan 26, 2015 at 12:12:43PM +0000, Arnaldo Carvalho de Melo wrote: > > Em Mon, Jan 26, 2015 at 10:27:11AM +0000, Will Deacon escreveu: > > > On Sun, Jan 25, 2015 at 03:56:52PM +0000, Russell King - ARM Linux wrote: > > > > On Sat, Jan 24, 2015 at 04:23:42PM -0600, Felipe Balbi wrote: > > > > > yeah, I'll try a few older kernels, also see if I can reproduce on other > > > > > boards. > > > > > > > > Perf works for me with CONFIG_FRAME_POINTER=y, but that's only for kernel > > > > space, and for userspace where the programs have been built for ARM mode > > > > with frame pointers. > > > > > > > > The kernel may work without CONFIG_FRAME_POINTER set, but I've never > > > > tested that, and I'd suggest that (given my experience looking at oops > > > > dumps) it's not all that reliable. > > > > > > > > Lastly, userspace without frame pointers is pretty much hopeless. > > > > > > FWIW, perf can now use libunwind for unwinding the userspace side of > > > things, so it's not quite as bad as it used to be. For the kernel side, > > > if the unwinder isn't working properly it would be nice to know *why*, > > > but I agree that it tends to be far flakier than the frame-pointer method. > > > > Any idea why, with userspace using frame pointers, perf doesn't go all > > the way from kernel to userspace main() (or whatever is the endpoint), > > as Russel stated? > > Did he state that? I thought he was just saying that he couldn't unwind > userspace when *not* using frame pointers, which requires you to link sorry, yeah I misunderstood, so all is good for kernel + userspace when both are built with frame pointers :-) "The only for kernel space" caught my attention, I thought that he said that it works only for the kernel with frame pointers, even with a userspace built with fp. - Arnaldo > a recent perf with a bleeding-edge libunwind. > > Will From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: Re: perf not capturing stack traces Date: Mon, 26 Jan 2015 09:29:32 -0300 Message-ID: <20150126122932.GB16629@kernel.org> References: <20150123195128.GE26557@saruman.tx.rr.com> <20150123205959.GD3073@kernel.org> <20150123223745.GJ26557@saruman.tx.rr.com> <20150124151204.GF3073@kernel.org> <20150124222342.GA26941@saruman.tx.rr.com> <20150125155651.GB11502@n2100.arm.linux.org.uk> <20150126102711.GC15598@arm.com> <20150126121243.GA16629@kernel.org> <20150126121621.GG15598@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail.kernel.org ([198.145.29.136]:33556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595AbbAZM33 (ORCPT ); Mon, 26 Jan 2015 07:29:29 -0500 Content-Disposition: inline In-Reply-To: <20150126121621.GG15598@arm.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Will Deacon Cc: Russell King - ARM Linux , Felipe Balbi , Peter Zijlstra , Tony Lindgren , Linux Kernel Mailing List , Ingo Molnar , Paul Mackerras , Linux OMAP Mailing List , Linux ARM Kernel Mailing List Em Mon, Jan 26, 2015 at 12:16:21PM +0000, Will Deacon escreveu: > On Mon, Jan 26, 2015 at 12:12:43PM +0000, Arnaldo Carvalho de Melo wrote: > > Em Mon, Jan 26, 2015 at 10:27:11AM +0000, Will Deacon escreveu: > > > On Sun, Jan 25, 2015 at 03:56:52PM +0000, Russell King - ARM Linux wrote: > > > > On Sat, Jan 24, 2015 at 04:23:42PM -0600, Felipe Balbi wrote: > > > > > yeah, I'll try a few older kernels, also see if I can reproduce on other > > > > > boards. > > > > > > > > Perf works for me with CONFIG_FRAME_POINTER=y, but that's only for kernel > > > > space, and for userspace where the programs have been built for ARM mode > > > > with frame pointers. > > > > > > > > The kernel may work without CONFIG_FRAME_POINTER set, but I've never > > > > tested that, and I'd suggest that (given my experience looking at oops > > > > dumps) it's not all that reliable. > > > > > > > > Lastly, userspace without frame pointers is pretty much hopeless. > > > > > > FWIW, perf can now use libunwind for unwinding the userspace side of > > > things, so it's not quite as bad as it used to be. For the kernel side, > > > if the unwinder isn't working properly it would be nice to know *why*, > > > but I agree that it tends to be far flakier than the frame-pointer method. > > > > Any idea why, with userspace using frame pointers, perf doesn't go all > > the way from kernel to userspace main() (or whatever is the endpoint), > > as Russel stated? > > Did he state that? I thought he was just saying that he couldn't unwind > userspace when *not* using frame pointers, which requires you to link sorry, yeah I misunderstood, so all is good for kernel + userspace when both are built with frame pointers :-) "The only for kernel space" caught my attention, I thought that he said that it works only for the kernel with frame pointers, even with a userspace built with fp. - Arnaldo > a recent perf with a bleeding-edge libunwind. > > Will From mboxrd@z Thu Jan 1 00:00:00 1970 From: acme@kernel.org (Arnaldo Carvalho de Melo) Date: Mon, 26 Jan 2015 09:29:32 -0300 Subject: perf not capturing stack traces In-Reply-To: <20150126121621.GG15598@arm.com> References: <20150123195128.GE26557@saruman.tx.rr.com> <20150123205959.GD3073@kernel.org> <20150123223745.GJ26557@saruman.tx.rr.com> <20150124151204.GF3073@kernel.org> <20150124222342.GA26941@saruman.tx.rr.com> <20150125155651.GB11502@n2100.arm.linux.org.uk> <20150126102711.GC15598@arm.com> <20150126121243.GA16629@kernel.org> <20150126121621.GG15598@arm.com> Message-ID: <20150126122932.GB16629@kernel.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Em Mon, Jan 26, 2015 at 12:16:21PM +0000, Will Deacon escreveu: > On Mon, Jan 26, 2015 at 12:12:43PM +0000, Arnaldo Carvalho de Melo wrote: > > Em Mon, Jan 26, 2015 at 10:27:11AM +0000, Will Deacon escreveu: > > > On Sun, Jan 25, 2015 at 03:56:52PM +0000, Russell King - ARM Linux wrote: > > > > On Sat, Jan 24, 2015 at 04:23:42PM -0600, Felipe Balbi wrote: > > > > > yeah, I'll try a few older kernels, also see if I can reproduce on other > > > > > boards. > > > > > > > > Perf works for me with CONFIG_FRAME_POINTER=y, but that's only for kernel > > > > space, and for userspace where the programs have been built for ARM mode > > > > with frame pointers. > > > > > > > > The kernel may work without CONFIG_FRAME_POINTER set, but I've never > > > > tested that, and I'd suggest that (given my experience looking at oops > > > > dumps) it's not all that reliable. > > > > > > > > Lastly, userspace without frame pointers is pretty much hopeless. > > > > > > FWIW, perf can now use libunwind for unwinding the userspace side of > > > things, so it's not quite as bad as it used to be. For the kernel side, > > > if the unwinder isn't working properly it would be nice to know *why*, > > > but I agree that it tends to be far flakier than the frame-pointer method. > > > > Any idea why, with userspace using frame pointers, perf doesn't go all > > the way from kernel to userspace main() (or whatever is the endpoint), > > as Russel stated? > > Did he state that? I thought he was just saying that he couldn't unwind > userspace when *not* using frame pointers, which requires you to link sorry, yeah I misunderstood, so all is good for kernel + userspace when both are built with frame pointers :-) "The only for kernel space" caught my attention, I thought that he said that it works only for the kernel with frame pointers, even with a userspace built with fp. - Arnaldo > a recent perf with a bleeding-edge libunwind. > > Will