From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: [PATCH net-next 1/3] perf: generalize perf_callchain Date: Thu, 25 Feb 2016 08:37:34 -0800 Message-ID: <56CF2DCE.5010501@fb.com> References: <1455767939-2700534-1-git-send-email-ast@fb.com> <1455767939-2700534-2-git-send-email-ast@fb.com> <20160225141859.GM6357@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , Ingo Molnar , Steven Rostedt , Wang Nan , Daniel Borkmann , Brendan Gregg , , To: Peter Zijlstra Return-path: In-Reply-To: <20160225141859.GM6357@twins.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2/25/16 6:18 AM, Peter Zijlstra wrote: > On Wed, Feb 17, 2016 at 07:58:57PM -0800, Alexei Starovoitov wrote: >> . avoid walking the stack when there is no room left in the buffer >> . generalize get_perf_callchain() to be called from bpf helper > > If it does two things it should be two patches. could have been two patches, but it will only add more churn to the same lines. what's the concern? >> Signed-off-by: Alexei Starovoitov >> --- >> arch/x86/include/asm/stacktrace.h | 2 +- >> arch/x86/kernel/cpu/perf_event.c | 4 ++-- >> arch/x86/kernel/dumpstack.c | 6 ++++-- >> arch/x86/kernel/stacktrace.c | 18 +++++++++++------- >> arch/x86/oprofile/backtrace.c | 3 ++- >> include/linux/perf_event.h | 13 +++++++++++-- >> kernel/events/callchain.c | 32 ++++++++++++++++++++------------ >> kernel/events/internal.h | 2 -- >> 8 files changed, 51 insertions(+), 29 deletions(-) > > And at the very least this should have had a note that it doesn't break > all the other archs that implement perf-callchain stuff. the cross-arch interface is two weak functions perf_callchain_kernel() and perf_callchain_user() and back into generic via perf_callchain_store(). Nothing changes there. The code speaks for itself. "non-x86 archs are not broken" would be a silly comment.